Aldehyde Oxidase Activity Research Articles

Emission of methylbutyric acid from Gypsophila paniculata L. during bud opening: Changes in amino acid catabolism

To elucidate the mechanism of methylbutyric acid emission which is responsible for the unpleasant odor of gypsophila inflorescences ( Gypsophila paniculata L. ‘Bristol Fairy’ and ‘Golan’), we investigated the activities of enzymes in the catabolic pathway of branched-chain amino acids. The continuous application of either 10 mM l-leucine, 10 mM l-isoleucine or 4.5 mM isovaleraldehyde increased the production of methylbutyric acids. When gypsophila inflorescences were treated with isovaleraldehyde, a large peak of isoamyl alcohol also appeared on the gas chromatogram. High activities of pyruvate decarboxylase (PDC), alcohol dehydrogenase (ADH) were detected in nonscented, tight and swollen buds, but the activities of these enzymes decreased in open florets. On the other hand, the activities of pyruvate dehydrogenase (PDH) and acyl-CoA hydrolase (ACH) increased during bud opening. The activities of aldehyde oxidase (AO) and aldehyde dehydrogenase (ALDH) were low throughout bud opening. These results indicate that the catabolism of branched-chain amino acids such as l-leucine in gypsophila inflorescences have two potential catabolic pathways. The first route, which finally converts l-leucine to isoamyl alcohol via isovaleraldehyde by PDC and ADH, is active before anthesis. The second route, which converts leucine to 3-methylbutyric acid via isovaleryl-CoA by PDH and ACH, becomes active in open florets. The alternation from the first to second route may correlate with the increase in emission of methylbutyric acids from open florets.

Characterization of the NifS-like Domain of ABA3 from Arabidopsis thaliana Provides Insight into the Mechanism of Molybdenum Cofactor Sulfuration

The molybdenum cofactor sulfurase ABA3 from Arabidopsis thaliana specifically regulates the activity of the molybdenum enzymes aldehyde oxidase and xanthine dehydrogenase by converting their molybdenum cofactor from the desulfo-form into the sulfo-form. ABA3 is a two-domain protein with an NH2-terminal domain sharing significant similarities to NifS proteins that catalyze the decomposition of l-cysteine to l-alanine and elemental sulfur for iron-sulfur cluster synthesis. Although different in its physiological function, the mechanism of ABA3 for sulfur mobilization was found to be similar to NifS proteins. The protein binds a pyridoxal phosphate cofactor and a substrate-derived persulfide intermediate, and site-directed mutagenesis of strictly conserved binding sites for the cofactor and the persulfide demonstrated that they are essential for molybdenum cofactor sulfurase activity. In vitro, the NifS-like domain of ABA3 activates aldehyde oxidase and xanthine dehydrogenase in the absence of the C-terminal domain, but in vivo, the C-terminal domain is required for proper activation of both target enzymes. In addition to its cysteine desulfurase activity, ABA3-NifS also exhibits selenocysteine lyase activity. Although l-selenocysteine is unlikely to be a natural substrate for ABA3, it is decomposed more efficiently than l-cysteine. Besides mitochondrial AtNFS1 and plastidial AtNFS2, which are both proposed to be involved in iron-sulfur cluster formation, ABA3 is proposed to be a third and cytosolic NifS-like cysteine desulfurase in A. thaliana. However, the sulfur transferase activity of ABA3 is used for post-translational activation of molybdenum enzymes rather than for iron-sulfur cluster assembly.

The Aldehyde Oxidase Gene Cluster in Mice and Rats: ALDEHYDE OXIDASE HOMOLOGUE 3, A NOVEL MEMBER OF THE MOLYBDO-FLAVOENZYME FAMILY WITH SELECTIVE EXPRESSION IN THE OLFACTORY MUCOSA

Mammalian molybdo-flavoenzymes are oxidases requiring FAD and molybdopterin (molybdenum cofactor) for their catalytic activity. This family of proteins was thought to consist of four members, xanthine oxidoreductase, aldehyde oxidase 1 (AOX1), and the aldehyde oxidase homologues 1 and 2 (AOH1 and AOH2, respectively). Whereas the first two enzymes are present in humans and various other mammalian species, the last two proteins have been described only in mice. Here, we report on the identification, in both mice and rats, of a novel molybdo-flavoenzyme, AOH3. In addition, we have cloned the cDNAs coding for rat AOH1 and AOH2, demonstrating that this animal species has the same complement of molybdo-flavoproteins as the mouse. The AOH3 cDNA is characterized by remarkable similarity to AOX1, AOH1, AOH2, and xanthine oxidoreductase cDNAs. Mouse AOH3 is selectively expressed in Bowman's glands of the olfactory mucosa, although small amounts of the corresponding mRNA are present also in the skin. In the former location, two alternatively spliced forms of the AOH3 transcript with different 3'-untranslated regions were identified. The general properties of AOH3 were determined by purification of mouse AOH3 from the olfactory mucosa. The enzyme possesses aldehyde oxidase activity and oxidizes, albeit with low efficiency, exogenous substrates that are recognized by AOH1 and AOX1. The Aoh3 gene maps to mouse chromosome 1 band c1 and rat chromosome 7 in close proximity to the Aox1, Aoh1, and Aoh2 loci and has an exon/intron structure almost identical to that of the other molybdo-flavoenzyme genes in the two species.

지부자 활성성분이 D-Galactosamine 투여에 의한 흰쥐의 간손상에 미치는 영향

지부자(Kochiae Fructus)의 생리활성물질 검색 및 간손상에 미치는 영향을 연구할 목적으로 실험동물에 지부자 추출물을 경구투여한 후 GaIN으로 간손상을 유발하여 혈액 및 간조직의 생화학적 변화를 관찰하고 free radical의 생성계와 해독계의 활성에 미치는 영향을 검토한 결과는 다음과 같다. GaIN 단독투여군은 대조군에 비하여 AST와 ALT가 증가하였으나, KFB, oleanolic acid, momordin Ic 투여군에서는 GaIN 단독투여군에 비해 유의적 감소를 보였다. 간조직의 지질과산화 함량은 GaIN 단독투여군이 대조군과 비교하여 증가하였고, KFM 200-GaIN군, KFB 200-GaIN군, momordin Ic 30-GaIN군과 oleanolic acid 30-GaIN군은 대조군에는 미치지 못하였으나 GaIN 단독투여군에 비해 현저히 감소하였다. XO, AO의 활성은 대조군보다 GaIN 단독투여군에서 유의적으로 증가하였으며, KFB 200-GaIN군, momordin Ic 30-GaIN군과 oleanolic acid 30-GaIN군의 XO와 AO의 활성은 GaIN 단독투여군보다 낮게 나타났다. 간조직 중의 GSH 농도는 GaIN 단독투여군이 대조군에 비해 현저히 감소하였고, KFB 200-GaIN군과 oleanolic acid 30-GaIN 군은 GaIN 단독투여군과 비교시 증가를 보였고, momordin Ic 30-GaIN군은 대조군에 가깝게 회복되었다. GaIN 단독투여군의 γ-GCS와 GR의 활성은 대조군에 비하여 유의한 감소를 보였고, momordin Ic 30-GaIN군의 γ-GCS의 활성은 대조군에는 미치지 못하였지만 GaIN 단독투여군에 비해 유의하게 개선되었다. KFM 200-GaIN군, KFB 200-GaIN군, momordin Ic 30-GaIN군과 oleanolic acid 30-GaIN군의 GR활성은 GaIN 단독투여군보다 유의한 증가를 보였다. GST 활성은 GaIN 단독투여군이 대조군에 비하여 현저한 감소를 나타내었고, KFM 200-GaIN군, KFB 200-GaIN군, momordin Ic 30-GaIN군과 oleanolic acid 30-GaIN군은 대조군 수준에는 못미쳤으나 GaIN 단독투여군보다 통계적으로 유의한 증가를 관찰할 수 있었다. SOD, catalase 및 GSH-Px의 활성은 대조군에 비하여 GaIN 단독투여군에서 감소를 보였고, SOD와 catalase 활성은 KFM, KFB와 oleanolic acid의 투여로 GaIN 단독투여군보다 높게 나타났다. 특히 momordin Ic 30-GaIN군의 SOD 활성은 대조군에 가깝게 개선되었다. GSH-Px의 활성은 KFM 200-GaIN군, KFB 200-GaIN군과 oleanolic acid 30-GaIN군은 대조군 수준에는 미치지 못하였으나 GaIN 단독투여군에 비해 현저히 증가하였고, 특히 momordin Ic 30-GaIN군은 대조군에 가깝게 증가되었다. 이상의 결과를 종합하여 볼 때 지부자로부터 분리한 momordin Ic가 GSH 농도를 증가시키고 활성산소 해독계에 관여하는 효소의 활성을 증가시킴으로서 GaIN으로 인한 간손상을 완화시키는 것으로 사료되어진다.

Kinetics and specificity of guinea pig liver aldehyde oxidase and bovine milk xanthine oxidase towards substituted benzaldehydes.

Molybdenum-containing enzymes, aldehyde oxidase and xanthine oxidase, are important in the oxidation of N-heterocyclic xenobiotics. However, the role of these enzymes in the oxidation of drug-derived aldehydes has not been established. The present investigation describes the interaction of eleven structurally related benzaldehydes with guinea pig liver aldehyde oxidase and bovine milk xanthine oxidase, since they have similar substrate specificity to human molybdenum hydroxylases. The compounds under test included mono-hydroxy and mono-methoxy benzaldehydes as well as 3,4-dihydroxy-, 3-hydroxy-4-methoxy-, 4-hydroxy-3-methoxy-, and 3,4-dimethoxy-benzaldehydes. In addition, various amines and catechols were tested with the molybdenum hydroxylases as inhibitors of benzaldehyde oxidation. The kinetic constants have shown that hydroxy-, and methoxy-benzaldehydes are excellent substrates for aldehyde oxidase (Km values 5x10(-6) M to 1x10(-5) M) with lower affinities for xanthine oxidase (Km values around 10(-4) M). Therefore, aldehyde oxidase activity may be a significant factor in the oxidation of the aromatic aldehydes generated from amines and alkyl benzenes during drug metabolism. Compounds with a 3-methoxy group showed relatively high Vmax values with aldehyde oxidase, whereas the presence of a 3-hydroxy group resulted in minimal Vmax values or no reaction. In addition, amines acted as weak inhibitors, whereas catechols had a more pronounced inhibitory effect on the aldehyde oxidase activity. It is therefore possible that aldehyde oxidase may be critical in the oxidation of the analogous phenylacetaldehydes derived from dopamine and noradrenaline.

Kinetics and specificity of guinea pig liver aldehyde oxidase and bovine milk xanthine oxidase towards substituted benzaldehydes.

Molybdenum-containing enzymes, aldehyde oxidase and xanthine oxidase, are important in the oxidation of N-heterocyclic xenobiotics. However, the role of these enzymes in the oxidation of drug-derived aldehydes has not been established. The present investigation describes the interaction of eleven structurally related benzaldehydes with guinea pig liver aldehyde oxidase and bovine milk xanthine oxidase, since they have similar substrate specificity to human molybdenum hydroxylases. The compounds under test included mono-hydroxy and mono-methoxy benzaldehydes as well as 3,4-dihydroxy-, 3-hydroxy-4-methoxy-, 4-hydroxy-3-methoxy-, and 3,4-dimethoxy-benzaldehydes. In addition, various amines and catechols were tested with the molybdenum hydroxylases as inhibitors of benzaldehyde oxidation. The kinetic constants have shown that hydroxy-, and methoxy-benzaldehydes are excellent substrates for aldehyde oxidase (Km values 5x10(-6) M to 1x10(-5) M) with lower affinities for xanthine oxidase (Km values around 10(-4) M). Therefore, aldehyde oxidase activity may be a significant factor in the oxidation of the aromatic aldehydes generated from amines and alkyl benzenes during drug metabolism. Compounds with a 3-methoxy group showed relatively high Vmax values with aldehyde oxidase, whereas the presence of a 3-hydroxy group resulted in minimal Vmax values or no reaction. In addition, amines acted as weak inhibitors, whereas catechols had a more pronounced inhibitory effect on the aldehyde oxidase activity. It is therefore possible that aldehyde oxidase may be critical in the oxidation of the analogous phenylacetaldehydes derived from dopamine and noradrenaline.

The effect of molybdate and tungstate in the growth medium on abscisic acid content and the Mo-hydroxylases activities in barley ( Hordeum vulgare L.)

The influence of molybdate and tungstate in the nutrient growth medium on the activities of the molybdo-enzymes, aldehyde oxidase (AO) and xanthine dehydrogenase (XDH) in barley ( Hordeum vulgare L.) plants was studied. Root AO and XDH activities were enhanced with increasing concentrations of molybdate in the nutrient medium, while AO and XDH activities in leaves were not significantly affected. Enzyme activities in root extracts rose slightly as the tungstate concentration was increased to 1 μM, but further elevation of tungstate concentration resulted in a reduction of AO and XDH activities. Leaf AO and XDH activities decreased with the addition of increasing amounts of tungstate in the medium. The general pattern of shoot ABA changes in response to exogeneously added molybdate and tungstate correlated with AO and XDH activity levels in roots. Shoot ABA concentration rose with increasing molybdate concentrations. Unexpectedly, similar results were obtained for exposure to tungstate, with the highest ABA level at metal concentration of 1 μmol/L. ABA contents in both the leaves and the roots declined substantially when plants were grown in media containing >10 μmol/L tungstate. The increased shoot ABA levels in response to molybdate and tungstate and the simultaneous enhancement of root AO and XDH activities, indicate that molybdate and tungstate influence ABA biosynthesis via regulation of root Mo-hydroxylases activities.

Effect of kaikasaponin III obtained from Pueraria thunbergiana flowers on serum and hepatic lipid peroxides and tissue factor activity in the streptozotocin-induced diabetic rat.

We investigated the effect of kaikasaponin III (KS-III) on Phase I and II enzymes and tissue factor (TF) activity to elucidate the pharmacological actions of this immunosuppressive saponin in the diabetic rat. This compound was obtained from the flower of Pueraria thunbergiana (Leguminosae) by chromatographic isolation. This crude drug (Puerariae Flos) has been used as a therapeutic agent for diabetes mellitus in traditional Korean medicine. KS-III prolonged the bleeding time and plasma clotting time in streptozotocin (STZ)-treated rats and increased the TF activity, suggesting that this compound has anti-thrombosis activity in STZ-induced rats. It also inhibited the formation of malondialdehyde (MDA) and hydroxy radicals in serum and liver, but promoted superoxide dismutase (SOD) activity. Low MDA concentrations and low xanthine oxidase and aldehyde oxidase activities were observed in the KS-III-treated rats, suggesting that such Phase I enzyme activities are the major source of lipid peroxidation. However, KS-III increased Phase II enzyme activities such as SOD, glutathione peroxidase, and catalase, suggesting the activation of free radical-scavenging enzymes. These results suggest that KS-III may exhibit its hypoglycemic and hypolipidemic effects by up-regulating or down-regulating antioxidant mechanisms via the changes in Phase I and II enzyme activities.

가자(Terminalia chebula) 추출물이 마우스의 생리활성에 미치는 영향

가자 추출물을 취하여 사람, 돼지, 쥐 및 개 등의 3% 적혈구용액으로 응집력시험을 행한 결과 7가지 적혈구 모두에 렉틴 활성이 나타났으며 <TEX>$LD_{50}$</TEX>는 390 mg/kg으로 측정되었다. 생리 활성에 대한 영향을 알아보고자 생체 내외인성 요인에 의한 친전자성 물질로 생체내에서 독작용, 노화, 발암 및 면역 억제작용을 유발하는 원인 물질인 free radical생성에 관여하는 효소인 XO 및 AO의 활성을 측정 한 결과, XO 에서는 일주일간 매일 300 mg/kg의 용량으로 가자 추출물을 투여한 군이 정상군보다 5배 증가되는 결과를 나타내었고 AO에서는 정상군보다 시료 투여군이 2배 증가되는 결과를 나타내었다 glutathione은 단백질이나 DNA합성, amino acid의 이동 반응 및 thiol기의 저장 등과 같은 생물학적으로 중요한 여러 가지 반응에 직접 관여하는 물질이다[16〕. 이에 간장 조직의 glutathione농도를 측정한 결과 간장 독성의 유발로 인한 효소 활성은 정상군에 비하여 1주간 매일 300 mg/kg의 용량으로 시료 투여한 군의 효소 활성이 79% 감소됨을 볼 수 있었다. 체내의 여러 가지 해독반응과정에 관여하는 GST효소활성을 측정 한 결과 정상군에 비해 1주간 매 일 300 mg/kg의 용량으로 시료 투여한 군이 66%정도 감소된다는 결과를 볼 수 있었다. glutathione 합성에 관여하는 <TEX>$\gamma$</TEX>-GCS의 활성과 산화형 glutathione을 환원형 glutathione으로 환원시키는 GR의 활성을 관찰한 결과 가자 추출물 투여군이 정상군보다 GR의 활성은 80% 감소되었고, 합성에 관여하는 <TEX>$\gamma$</TEX>-GCS의 활성은 정상군과 비교할 때 약간의 감소만을 나타내 glutathione함량 변동에 크게 영향을 미치지 않는 것으로 생각된다. In this study, we investigated the effect of water, extract of Terminalia Chebula (TC) on physiological activity in mice. TC water extract showed hemagglutination against several different types of red blood cells. <TEX>$LD_{50}$</TEX> of TC extract was 390 mg/kg (po). Treatment of TC water extract orally administered 200, 300 mg/kg daily for one week. Hepatic cytosolic enzymes, xanthine oxidase and aldehyde oxidase activities were significantly increased comparison with normal group. Treatment of TC water extract increased hepatic malondialdehyde (MDA) formation, and reduced glutathione content. We also found that the decreased activities of glutathione S-transferase and glutathione reductase but was not affected activities of <TEX>$\gamma$</TEX>-glutamylcysteine synthetase after treatment of TC water extract. These results suggested that increase of the hepatic lipid peroxide is caused by glutathione reduction.

가자(Terminalia chebula) 추출물이 흰쥐의 간장 활성에 미치는 영향

가자 추출물을 흰쥐에 일정량 투여한 후 간장에 미치는 영향을 관찰할 목적으로 여러 가지 효소량의 변동을 검토하였다. 간 손상의 지표로 사용되는 AST, ALT활성을 측정한 결과 AST, ALT모두에서 정상군보다 300 mg/kg의 용량으로 2주 시료 투여한 군의 함량이 2배 이상 증가되는 것으로 나타났다. 가자 추출물이 지질과산화물 생성에 미치는 효과를 관찰한 결과, 300 mg/kg의 용량으로 2주 시료 투여한 군함량이 정상군에 비해 135.43%, 173.9% 정도 증가하는 결과를 나타내었다. 간 조직의 지질과산화물 반응에 관여하는 것으로 알려진 XO, AO, AD 및 AH활성에 대한 효과를 관찰한 결과 마이크로솜 분획에 존재하는 AD, AH의 활성은 저해 효과가 없었고, 세포질 효소인 XO, AO의 활성은 300 mg/kg의 용량으로 2주 시료 투여한 군 함량이 정상군에 비해 약 2배 증가됨을 볼 수 있었다. 가자 추출물에 의한 간 조직중 glutathione농도에 미치는 영향에 대해 관찰한 결과 2주 동안 300 mg/kg의 용량으로 투여한 군의 glutathione농도는 정상군에 비해 약 75% 감소하는 것으로 나타났다 가자 추출물 투여 후 glutathione의 함량 감소를 경감시키는 기전을 알아볼 목적으로 glutathione 합성에 관여하는 <TEX>$\gamma$</TEX>-GCS의 활성과 산화형 glutathione을 환원형 glutathione으로 환원시키는 GR의 활성을 관찰한 결과 정상군에 비해 GR이 56.6%, <TEX>$\gamma$</TEX>-GCS가 6.7% 정도 감소하는 것으로 나타났다. 이러한 glutathione의 함량 변동은 산화형 glutathione을 환원형 glutathione으로 환원시키는 GR의 활성에 영향을 주어 나타나는 결과로 생각된다. 가자 추출물이 지질과산화의 해독계에 미치는 영향을 관찰할 목적으로 catalase, GP 및 SOD의 활성을 측정한 결과 catalase, GP의 활성은 각각 77.5%, 64.3% 감소하는 결과를 나타냈으며, SOD의 활성은 정상군에 비해 약 3배 증가하는 것으로 나타났다. In this study, we investigated the effect of Teminalia Chebula (TC) water extract on liver in Rat. Treatment of TC water extract was orally administered 200, 300 mg/kg daily for one week and two weeks. The clinical parameters of serum, values of AST, ALT showed significantly higher than in normal group. Xanthine oxidase and aldehyde oxidase activities were significantly increased comparison with normal group. Microsomal enzymes, aminopyrine N-demethylase and aniline hydroxylase were not affected. Water extract of TC also increased hepatic rnalondialdehyde formation and reduced glutathione content. We also found that water extract of TC decreased activities of glutathione S-transferase and glutathione reductase but was not affected activities of <TEX>$\gamma$</TEX>-glutamylcysteine synthetase Thus, it seems that the water extract of TC induced decrease of oxygen free radical scavenger, glutathione content by inhibition of glutathione reductase which may reform oxidized glutathione to reduced glutathione.

Circadian Rhythms of Hepatic Molybdenum Hydroxylases Activities in the Rat

The objectives of this study is to investigate the occurrence of circadian rhythms with molybdenum hydroxylases as many other enzymes were found to show this phenomenon. The specific activities of molybdenum hydroxylases, namely; aldehyde oxidase and xanthine oxidase were measured in partially purified ammonium sulfate fractions of adult rat liver eight times daily at equal intervals. The activity of aldehyde oxidase was found to vary markedly with the substrates used (3-methylisoquinoline and phthalazine). The highest enzyme activity with both substrates was observed at 1500 hr, whereas the lowest activity occurred at 0900 hr. There were highly statistically significant (P < 0.0005) differences between the maximum and minimum activities. Circadian variation was also observed in xanthine oxidase activity when xanthine was used as a substrate. Two main maximum peaks appeared at 1500 hr and 2100 hr, and the minimum activity peak was shown at 0300 hr. The difference between the rhythmic extremes was statistically significant (P < 0.0005). These results indicate that some factors such as hormones, may be responsible for the circadian variations exhibited in aldehyde oxidase and xanthine oxidase activities.

Ziprasidone metabolism, aldehyde oxidase, and clinical implications.

Ziprasidone (Geodon, Zeldox), a recently approved atypical antipsychotic agent for the treatment of schizophrenia, undergoes extensive metabolism in humans with very little (<5%) of the dose excreted as unchanged drug. Two enzyme systems have been implicated in ziprasidone metabolism: the cytosolic enzyme, aldehyde oxidase, catalyzes the predominant reductive pathway, and cytochrome P4503A4 (CYP3A4) is responsible for two alternative oxidation pathways. The involvement of two competing pathways in ziprasidone metabolism greatly reduces the potential for pharmacokinetic interactions between ziprasidone and other drugs. Because CYP3A4 only mediates one third of ziprasidone metabolism, the likelihood of interactions between ziprasidone and CYP3A4 inhibitors/ substrates is low. Furthermore, aldehyde oxidase activity does not appear to be altered when drugs or xenobiotics are coadministered. Aldehyde oxidase, a molybdenum-containing enzyme, catalyzes the oxidation of N-heterocyclic drugs such as famciclovir and zaleplon, in addition to reducing some agents such as zonisamide. Both reactions can occur simultaneously. Although in vitro inhibitors of aldehyde oxidase have been identified, there are no reported clinical interactions with aldehyde oxidase inhibitors or inducers. There is no evidence of genetic polymorphism in aldehyde oxidase, and thus it not surprising that ziprasidone exposure demonstrates unimodality in humans. Aldehyde oxidase is unrelated to the similarly named enzyme aldehyde dehydrogenase, which is predominantly responsible for the oxidation of acetaldehyde during ethanol metabolism. Consequently, it is unlikely that there would be any pharmacokinetic interaction between ethanol and ziprasidone.

Mutations in the molybdenum cofactor biosynthetic genes MOCS1, MOCS2, and GEPH.

Molybdenum cofactor deficiency in humans results in the loss of the activity of molybdoenzymes sulfite oxidase, xanthine dehydrogenase, and aldehyde oxidase. The resultant severe phenotype, which includes progressive neurological damage leading in most cases to early childhood death, results primarily from the deficiency of sulfite oxidase. All forms of molybdenum cofactor deficiency are inherited as autosomal recessive traits. The cofactor is an unstable reduced pterin with a unique four-carbon side chain, synthesized by a complex pathway that requires the products of at least four different genes (MOCS1, MOCS2, MOCS3, and GEPH). Disease-causing mutations have been identified in three of these genes: MOCS1, MOCS2, and GEPH. MOCS1 and MOCS2 have a bicistronic architecture; i.e., each gene encodes two proteins in different open reading frames. The protein products, MOCS1A and B and MOCS2A and B, are expressed either from different mRNAs generated by alternative splicing or by independent translation of a bicistronic mRNA. The gephyrin protein, encoded by a third locus, is required during cofactor assembly for insertion of molybdenum. A total of 32 different disease-causing mutations, including several common to more than one family, have been identified in molybdenum cofactor-deficient patients and their relatives.

Inter-strain variability in aldehyde oxidase activity in the mouse

Aldehyde oxidase (AO) is a cytosolic enzyme expressed predominantly in the liver. AO is involved in the metabolism of many xenobiotics of pharmacological and toxicological importance including antivirals (famciclovir), antimalarials (quinine) and anticancer drugs (5-fluoro-2-pyrimidine and methotrexate). The aim of this study was to characterize AO activity in different strains of mice using two different substrates. AO activity in the cytosolic fraction was characterized using the metabolism of N-[2-(dimethylamino)ethyl]acridine-4-carboxamide (DACA), a novel antitumor drug, to form DACA-9(10H)-acridone (quantified by HPLC with fluorescence detection) and benzaldehyde to form benzoic acid (quantified spectrophotometrically). Characterization of mouse AO activity with DACA showed 15-fold variation in K m, 10-fold variation in apparent V max and twofold differences in intrinsic clearance. Nude mice and C129/C57 had the highest intrinsic clearance (0.66 and 0.l53 ml/min per mg protein, respectively). Nude mice cleared DACA faster than nude tumor bearing mice by a factor of 2. Male Swiss CD had higher intrinsic clearance than female Swiss CD (0.36 and 0.28 ml/min per mg protein). A similar pattern of enzyme activity was observed with benzaldehyde; however, the extent of variation was less than that found with DACA. In conclusion, our results show that there are both strain and gender differences in AO activity. These differences are better detected by DACA. Furthermore, these results suggest caution when extrapolating the data obtained from mouse AO studies to humans.

Molecular characterization of the amplified aldehyde oxidase from insecticide resistant Culex quinquefasciatus.

Primary structural information including the complete nucleotide sequence of the first insect aldehyde oxidase (AO) was obtained from the common house mosquito Culex quinquefasciatus (Say) through cloning and sequencing of both genomic DNA and cDNA. The deduced amino-acid sequence encodes a 150-kDa protein of 1266 amino-acid residues, which is consistent with the expected monomeric subunit size of AO. The Culex AO sequence contains a molybdopterin cofactor binding domain and two iron-sulfur centres. A comparison of the partial sequences of AO from insecticide resistant and susceptible strains of C. quinquefasciatus shows two distinct alleles of this enzyme, one of which is amplified in the insecticide resistant strain on a 30-kb DNA amplicon alongside two resistance-associated esterases. The amplified AO gene results in elevated AO activity in all life stages, but activity is highest in 3rd instar larvae. The elevated enzyme can be seen as a separate band on polyacrylamide gel electrophoresis. The role of AO in xenobiotic oxidation in mammals and the partial inhibition of elevated AO activity by a range of insecticides in Culex, suggest that this AO may play a role in insecticide resistance.

Kalopanaxsaponin A from Kalopanax pictus, a potent antioxidant in the rheumatoidal rat treated with Freund's complete adjuvant reagent

The stem bark of Kalopanax pictus is an anti-rheumatoidal arthritis drug in Oriental medicine. In the rheumatoidal rat, induced by Freund's complete adjuvant (FCA) reagent, we investigated the effects of hederagenin monodesmosides of K. pictus on oxidative stress and hepatic drug-metabolizing enzymes. Kalopanaxsaponin-A (KPS-A) significantly decreased malondialdehyde formation and the activities of xanthine oxidase and aldehyde oxidase of hepatic non-microsomal systems in FCA reagent-treated rats. In addition, increased activity levels of superoxide dismutase, catalase and glutathione peroxidase were also observed. The effects of KPS-A were more potent than the effects of KPS-I. These results suggested that KPS-A, extracted from K. pictus, could reduce rheumatoidal syndromes through antioxidative mechanisms.

Transport and accumulation rates of abscisic acid and aldehyde oxidase activity in Pisum sativum L. in response to suboptimal growth conditions

Pea plants (Pisum sativum L.) grown initially in nutrient solutions with adequate nitrogen supply (4 mM NO3-) were transferred to solutions containing salt (50 or 100 mM NaCl), ammonium (4 mM) or a low nitrogen supply (0.4 mM NO3-). No changes of abscisic acid (ABA) content were found in roots of stressed pea plants 9 d after the beginning of the treatments; however, accumulation of ABA in the leaves was observed. Old leaves accumulated ABA to a higher extent than young leaves. Accumulation of ABA in leaves of ammonium-fed plants and plants grown under low nitrogen supply occurred in the absence of both increased ABA xylem loading rate and enhanced aldehyde oxidase (AO, EC 1.2.3.1) activity in roots. Enhanced leaf AO activity was observed in all treatments, with the highest increase in old leaves. Among the three AO isoforms (AO-1, AO-2 and AO-3) detected in extracts of pea leaves, the lowest one AO-3 (highest mobility in the gel) correlated with ABA production and showed the highest increment in response to the treatments. The increase of AO activity detected in leaves after 2 weeks of stress application was less prominent than after 9 d, suggesting a transient enhancement of ABA production following the onset of stress. An increase of ABA xylem loading rate as well as AO root activity 4 d and 9 d after application of the treatments was observed only in salt-treated plants followed by a decrease after 14 d in 100 mM NaCl. Decreased cytokinin (trans-zeatin riboside) delivery rate into the xylem sap was observed in all treatments. The role of abscisic acid and cytokinins as positive and negative growth signals, as well as the involvement of root-generated ABA on ABA accumulation in leaves is discussed.

Transport and accumulation rates of abscisic acid and aldehyde oxidase activity in Pisum sativum L. in response to suboptimal growth conditions

Pea plants ( Pisum sativum L.) grown initially in nutrient solutions with adequate nitrogen supply (4 mM NO 3− ) were transferred to solutions containing salt (50 or 100 mM NaCl), ammonium (4 mM) or a low nitrogen supply (0.4 mM NO 3− ). No changes of abscisic acid (ABA) content were found in roots of stressed pea plants 9 d after the beginning of the treatments; however, accumulation of ABA in the leaves was observed. Old leaves accumulated ABA to a higher extent than young leaves. Accumulation of ABA in leaves of ammonium‐fed plants and plants grown under low nitrogen supply occurred in the absence of both increased ABA xylem loading rate and enhanced aldehyde oxidase (AO, EC 1.2.3.1) activity in roots. Enhanced leaf AO activity was observed in all treatments, with the highest increase in old leaves. Among the three AO isoforms (AO‐1, AO‐2 and AO‐3) detected in extracts of pea leaves, the lowest one AO‐3 (highest mobility in the gel) correlated with ABA production and showed the highest increment in response to the treatments. The increase of AO activity detected in leaves after 2 weeks of stress application was less prominent than after 9 d, suggesting a transient enhancement of ABA production following the onset of stress. An increase of ABA xylem loading rate as well as AO root activity 4 d and 9 d after application of the treatments was observed only in salt‐treated plants followed by a decrease after 14 d in 100 mM NaCl. Decreased cytokinin ( trans‐ zeatin riboside) delivery rate into the xylem sap was observed in all treatments. The role of abscisic acid and cytokinins as positive and negative growth signals, as well as the involvement of root‐generated ABA on ABA accumulation in leaves is discussed.

Individual variation in hepatic aldehyde oxidase activity.

Aldehyde oxidase (AO) is a molybdo-flavo enzyme expressed predominantly in the liver, lung, and kidney. AO plays a major role in oxidation of aldehydes, as well as oxidation of various N-heterocyclic compounds of pharmacological and toxicological importance including antiviral (famciclovir), antimalarial (quinine), antitumour (methotrexate), and nicotine. The aim of this study was to investigate cytosolic aldehyde oxidase activity in human liver. Cytosolic AO was characterised using both the metabolism of N-[(2-dimethylamino)ethyl] acridine-4-carboxamide (DACA) and benzaldehyde to form DACA-9(10H)-acridone (quantified by HPLC with fluorescence detection) and benzoic acid (quantified spectrophotometrically). Thirteen livers (10 female, 3 male) were examined. The intrinsic clearance (Vmax/Km) of DACA varied 18-fold (0.03-0.50 m/min/mg). Vmax ranged from 0.20-3.10 nmol/ min/mg, and Km ranged from 3.5-14.2 microM. In the same specimens, the intrinsic clearance for benzaldehyde varied 5-fold (0.40-1.8 ml/min/mg). Vmax ranged from 3.60-12.6 nmol/min/mg and Km ranged from 3.6-14.6 microM. Furthermore, there were no differences in AO activity between male and female human livers, nor was there any relationship to age of donor (range 29-73 years), smoking status, or disease status. In conclusion, our results showed that there are variations in AO activity in human liver. These variations in aldehyde oxidase activity might reflect individual variations or they might be due to AO stability during processing and storage.

Daily Rhythm in Hepatic and Renal Aldehyde Oxidase and Xanthine Oxidase in Male and Female Uromastyx microlepis

The activities of aldehyde oxidase and xanthine oxidase were determined in partially purified preparations from livers and kidneys of male and female Dhubb, Uromastyx microlepis, four times daily at equal intervals. The maximum activity of male and female hepatic aldehyde oxidase appeared at 2100 h, whereas the minimum activity was observed at 0300 h, using phthalazine and 3-methylisoquinoline as substrates. The differences between maximum and minimum activity were statistically significant (P < 0.05). No fluctuation was observed in male renal aldehyde oxidase activity with phthalazine, whereas female enzyme showed significant daily variations (P < 0.0005). Using 3-methyliosoquinoline as a substrate, both male and female renal aldehyde oxidase showed drop in activity at 1500 h, and the differences between minimum and maximum were significant (P < 0.0005). Circadian variations in male and female renal xanthine oxidase activities were observed using xanthine as a substrate. The main peak appeared at 0300 h and minimum activity from 1500 to 2100 h, and the difference between rhythmic extremes was statistically significant (P < 0.03).