Hydrazine Analogues Research Articles

Anomeric Answer to Sulfenamide Stability and α-Nucleophilicity.

The S-N bond remains a synthetically challenging motif for organic chemists to access. The problem arises from instability in many sulfenamide derivatives, which has led to fewer S-N bond surrogate molecules compared to their hydroxylamine (NH2OH) and hydrazine (NH2NH2) analogues. In turn, sulfenamides have often been omitted in studies regarding α-nucleophilicity. Herein, we provide factors responsible for the stability of the sulfenamide motif and provide new insights on the nucleophilic properties of sulfenamides as they relate to the α-effect.

Synthesis, spectroscopic characterizations and cytotoxic activities of some novel 1,2-bis-(tetrasubstituted-benzylidene) hydrazine analogues

ABSTRACT. The present work describes an efficient and convenient synthesis of a library of novel 1, 2-bis-(tetrasubstituted-benzylidene) hydrazine an analogue (3-7) 1,2-bis (3-methoxy-2-hydroxybenzlidene) hydrazine (3) and 1,2-bis (6-bromo-3-methoxy 2-hydroxybenzylidene) hydrazine (4), were obtained via opening of ester coumarin derivatives (1 and 2) with hydrazine hydrate under reflux. Diazotization of compound 4 with aryldiazonium chloride led to the formation of 1,2-bis (6-bromo-5-arylazo-3-methoxy-2-hydroxybenzylidene) hydrazine (6a,b). Acetylation of compounds 4 and 6a with acetic anhydride afforded the corresponding 1,2-bis (6-bromo-5-substituted-3-methoxy-2-acetoxy benzylidene) hydrazines (5 and 7). The cytotoxicity screening of some synthesized 1,2-bis (tetra substituted benzylidene) hydrazines (4-7) against breast cancer cell lines (MCF-7), and it was found several active compounds. Meanwhile compound 5 exhibited cytotoxic activity compared to reference drug. The DNA flow cytometry on MCF-7 cells of compound 5 was determined, it was found to cause G2/M phase arrest and induce apoptosis in all G1/M phases. In addition, compound 5 has been tested in other trials against aromatase inhibitors and tyrosinase inhibitors.
 KEY WORDS: Synthesis, Hydrazine derivatives, 1H NMR, Mass spectra, MCF-7 cell lines, Cytotoxicity
 Bull. Chem. Soc. Ethiop. 2023, 37(6), 1503-1520.DOI: https://dx.doi.org/10.4314/bcse.v37i6.16

An experimental investigation of slat-screens to mitigate fluid sloshing in microgravity

The new age of space exploration has brought forth growing implications of space debris connected to satellites, and as such on-orbit satellite refuelling is an area of active research. To refuel a satellite on-orbit, a servicing satellite transfers propellant to the empty fuel tank of the satellite being serviced. A significant impediment to such a practice is the development of fluid sloshing motion during this process. This paper presents a study of the use of slat screens to damp fluid sloshing motion during a simulated refuelling of a fuel tank under microgravity conditions. There is particular interest in the sloshing motion developed due to internal forces produced from fluid injection. Two fluids, each analogous to common spacecraft propellants; hydrazine and liquid oxygen (LOX), were tested under a microgravity environment created by parabolic manoeuvres aboard the National Research Council of Canada's (NRC) Falcon 20 research aircraft. The experimental setup included three test chambers, two of which contained a perforated and a single-entry slat screen, designed to mitigate sloshing. High-speed imaging of fluid sloshing development within the test chambers was captured and analysed. The rate of fuelling was varied during subsequent parabolas to 25%, 50% and 75% of the internal volume capacity (1 L). Based on initial findings, statistical differences exist (P<0.05) in the latency for the LOX analogue, to reach 75% and 95% of the total chamber height. Differences were observed specifically between the control chamber and the chamber with perforated slat screens. Furthermore, qualitative observations of the hydrazine analogue fluid motion in microgravity show that at 50% fill ratio, slat screens result in a plateau of maximum fluid height. This suggests that slat screens may be an effective method of damping fluid sloshing motion and could be adopted by industry in the pursuit of on-orbit refuelling and the development of more sustainable spacecraft.

Design, synthesis, and anticancer evaluation of acetamide and hydrazine analogues of pyrimidine

AbstractA library of acetamide and hydrazine analogues were generated on the pyrimidine ring through a multistep reaction starting from 5‐nitro‐pyrimidine‐4,6‐diol and pyrimidine‐4,6‐diol, respectively. The synthesized analogues were screened for in vitro cytotoxic activity against various human cancer cell lines like HCT‐1 and HT‐15 (colon), MCF‐7(breast), PC‐3 (prostrate), SF268 (CNS) using MTT method. From the bioassay results, it was observed that even though many of the synthesized derivatives exhibited a good potency against various screened cancer cell lines, compound 14a from the acetamide series was found to show potent anticancer activity on all the tested cancer cell lines with IC50 value of 0.36μM on CNS cell line and 1.6μM on HT‐21 cell line, and compound 19xxi from hydrazine series of pyrimidine showed potent activity against three tested cancer cell lines with IC50 value of 0.76μM on HT‐29 cell line, 2.6μM on HCT‐15, and 3.2μM on MCF‐7 cell line.

Development and validation of chiral HPLC method for quantitative determination of hydrazine analogue in Argatroban monohydrate

Abstract Argatroban is an anticoagulant which is used as direct thrombin inhibitor. It consists of hydrazine analogue, which is probably similar to Argatroban. The single HPLC method is already reported in to United States Pharmacopeia (USP). In that method, Argatroban peak eluted as R-Argatroban and S-Argatroban while hydrazine analogue eluted as P1 and P2 peaks. The P2 peak of Hydrazine analogue is eluted as retention time of R-Argatroban peak. Therefore it was difficult to determine the accurate concentration of Hydrazine analogue in to Argatroban. The existing method is longer run time up to 102 min. The present HPLC method shows appropriate resolution between hydrazine analogue and Argatroban. The total run time reduces up to 40 min, which is a ∼2.5 time lesser than reported in literature. In present method hydrazine analogue and Argatroban are eluted to be 9.0 min and 12.5 min respectively. The effective chromatographic separations are achieved on YMC chiralart cellulose-SC, 250×4.6 mm, 5μ column and normal phase with linear elution. The mobile phase was uniform mixture of methanol, acetonitrile, dichloromethane, trifluoroacetic acid, triethylamine with ratio of 30:50:920:3:4 and delivered flow rate 0.7 mL/min. Analysis is performed on UV/PDA detector with detection wavelength is adjusted at 259 nm. The injection volume is 5μL and column oven temperature is 35°C. The present method is accurate and precise as well as linear in the range of LOQ to 150 % level. The finalized concentration of hydrazine analogue for limit of detection and quantitation is 0.003 and 0.010%. The correlation coefficient of hydrazine analogue is 0.99947. The recovery for ranged between 100.00 to 103.29%. In robustness study for of mobile phase flow rate and column oven temperature, no significant changes are observed in system suitability parameters and result. This method has been developed and validated using the ICH guideline Q2(R1).The new method is sensitive, precise, accurate, and rapid; it also qualifies all the criteria of linearity, stability, as well as robustness.

Synthesis and biological properties of novel 1-methyl-2-(2-(prop-2-yn-1-yloxy)benzylidene) hydrazine analogues

Synthesis and biological properties of novel 1-methyl-2-(2-(prop-2-yn-1-yloxy)benzylidene) hydrazine analogues

The Exciting Chemistry of 1,1-Diamino-2,2-dinitroethene and 1-Amino-1-hydrazino-2,2-dinitroethene.

1,1-Diamino-2,2-dinitroethene (FOX-7) is a relatively new highly energetic material, with good explosive performance and low sensitivity against mechanical stimuli and thermal stress. Therefore, on the one hand, FOX-7 is very stable and a starting material with fairly low reactivity. On the other hand, chlorosulfonyl isocyanate ClSO2NCO is a very reactive reagent and represents a highly activated form of isocyanic acid HNCO. New derivatives of FOX-7 and its hydrazine analogue 1-amino-1-hydrazino-2,2-dinitroethene, as well as unusual potassium salts, are described. Besides the usual spectroscopic characterization, the structures of all compounds were investigated and discussed by single-crystal X-ray diffraction. The compounds demonstrate good thermal stabilities, very high densities, and excellent sensitivity values. The heats of formation were calculated, and together with the room-temperature densities, the energetic parameters were estimated. The compounds are potential candidates as insensitive high-energy-density materials and starting materials for further chemistry.

Study of the Ammonia Oxidation Mechanism By a Normal Pusle Voltammetry

Although ammonia is expected as the next generation of energy medium, even platinum, which is a relatively active ammonia oxidation (AO) catalyst, have an insufficient performance for direct ammonia fuel cells (DAmFCs) operating below 100°C. Highly active AO catalysts at low temperatures needs to be developed in order to use ammonia as a fuel for DAmFCs. AO mechanism on platinum is reported as follows: After NH3 is adsorbed on the platinum surface, the AO proceeds via two competitive paths. One is the formation of hydrazine analogues, followed by the oxidation of the analogues to release N2 molecules. The other is the oxidation of an ammonia molecule to form nitrogen atoms adsorbed onto the surface of platinum (Nads) known as poisoning species. However, after the surface of the platinum is covered with Nads, the elimination process of Nads is not known. In this study, the elimination process was studied by a normal pulse voltammetry. 33.6 wt% Pt/MWCNT (average particle size: 5.57 ± 0.11 nm) catalyst was synthesized by a microwave polyol method. A 2 mg of Pt/MWCNT was suspended in 1 mL of Pt/MWCNT-0.1 wt% Nafion-MeOH by ultrasonication for 10 min. 10 μL of the suspension was cast onto a glassy carbon (GC) disk electrode (6 mm φ), followed by drying for 1 h in air. Electrochemical measurements were performed with a conventional three electrode system equipped with the modified GC electrode, an Au wire counter electrode and a reversible hydrogen electrode (RHE) in 0.1 M KOH or 0.1 M NH3-0.1 M KOH. The normal pulse voltammetry was performed as follows: After the Nads was formed by applying 0.6 V for 180 s, E recover (V) was applied for various times (1 s，5 s，10 s，20 s，60 s, and 180 s) to eliminate Nads. Then, the AO current at 0.6 V after 1 s was used as an indicator for the amount of Nads poisoning. Fig. 1 shows the dependence of AO current at 0.6 V after 1 s on recovery potential. The AO current gradually recovered by maintaining the potential below 0.4 V vs. RHE, indicating that the adsorbed N atoms were eliminated from the catalyst surface. It took a few minutes to recover the AO current. In addition, the decrease in potential accelerated the recovery of the AO current, especially below 0.3 V vs. RHE. The final percentage of the recovery increased with a decrease in the potential. The recovery rates below 0.25 V called hydrogen adsorption/desorption region increased with decreasing potential, probably due to the reduction of Nads. The time dependence of the recovery rate was analyzed by the sum of two exponentials, suggesting that the fast and slow reactions exists in the recovery process. Figure 1

Synthesis, Characterization, and Biological Evaluation of certain 6-methyl-2(3H)-benzo-1, 3-thiazolyl-1'-ethylidene-2-(o, p- Substituted Acetophenones) Hydrazine Analogs

In the present study, five new derivatives (GG4 to GG8) of benzothiazoles were synthesized and evaluated against Staphylococcus aureus (MTCC 737), Pseudomonas aeruginosa (MTCC 424), Escherichia coli (MTCC 1687), and yeast-like fungi Candida tropicalis. p-Toluidine on treatment with ammonium thiocynate formed 2-benzothiazolamines (II), which on reaction with hydrazine hydrate formed a hydrazino derivative (III). Compounds GG4 to GG8 were synthesized by reacting the hydrazine derivative with different acetophenones. All the synthesized compounds were identified by IR and 1H-NMR, and antimicrobial activity was performed on the synthesized compounds. Presence of NO2, Br, OCH3, and Cl groups to the substituted benzothiazole enhanced the antibacterial and antifungal activities.

Novel GABA-AT inhibitors: QSAR and docking based virtual screening of phenyl substituted β-phenyl ethylidene hydrazine analogues

In the present study, Lamarckian genetic algorithm (LGA) based docking (AutoDock 4.0), k-nearest neighbor molecular field analysis (kNN-MFA) based 3D-QSAR, fragment and knowledge based approach were used to generate and screen a virtual library. Three analogues of β-phenylethylidene hydrazine (PEH) were designed as novel GABA-AT inhibitors. The docking interactions of N-[(1E) 2-phenylethylidene]pyridin-2-amine (S 4 ), (2E)-1-phenyl-2-(2-phenylethylidene)hydrazine (S 8 ) and (1E)-1-ethylidene-2-phenylhydrazine (S 21 ) with Lys 329 appears to be in close proximity and explains the high GABA-AT selectivity observed.

Reaction between the anesthetic agent propofol and the free radical DPPH˙ in semiaqueous media: Kinetics and characterization of the products

The reaction of the free radical diphenylpicrylhydrazyl (DPPH˙) with the anesthetic agent 2,6-diisopropylphenol (propofol, PPF) was investigated in buffered hydroalcoholic media. The kinetics was followed using a stopped-flow system. DPPH˙ was reduced to the hydrazine analogue DPPH–H with a measured stoichiometry (DPPH˙/PPF) of 2. The main product of the reaction, 3,5,3′,5′-tetraisopropyl-(4,4′)-diphenoquinone (PPFDQ) was isolated by chromatography and its structure was fully characterized. The reaction mechanism was inferred from the stoichiometry, kinetics, and product identification. The first step, which primarily determines the kinetics, is the reaction of DPPH˙ with PPF to produce DPPH–H and the PPF radical. The rate constant was found to be 31.8, 207, and 908 M − 1 s − 1 at pH 6.4, 7.4, and 8.4, respectively. The pH dependence is indicative of a higher reactivity of the phenolate form of PPF. Then, PPF radicals combine to form dipropofol, which is quickly oxidized to PPFDQ by the remaining DPPH˙. This reaction scheme is corroborated by numerical simulations of the kinetics. In the course of this study we also disclosed an unexpected effect, the photochemical degradation of PPFDQ. The need to compare antioxidants on a kinetics basis is again emphasized. In our hands, PPF presents a significantly weaker reactivity than Trolox.

Kinetics of the reaction between the antioxidant Trolox? and the free radical DPPH? in semi-aqueous solution

Reaction of the free-radical diphenylpicrylhydrazyl (DPPH(.)) with Trolox (TrOH) was investigated in buffered hydroalcoholic media by using a stopped-flow system. DPPH was reduced to the hydrazine analogue DPPH-H with a measured stoichiometry of about 2. DPPH-H was characterized by an acid-base equilibrium (pKa = 8.6). Time-resolved absorption spectra recorded with an excess of either TrOH or DPPH indicated that no significant amount of the TrO radical was accumulated. The TrO radical formed in a first step further reacted quickly with DPPH(.). For 1 : 1 ethanol-buffer mixtures at pH 7.4, the bimolecular rate constants of the first and second steps were 1.1 x 10(4) M(-1) s(-1) and 2 x 10(6) M(-1) s(-1), respectively. A significant increase of the measured rate constant was observed for ethanol-buffer solutions as compared to ethanol. The rate was also increased at higher pH. A deuterium isotopic effect of 2.9 was measured. These data are discussed with regards to mechanisms involving either electron or proton exchange as rate determining steps in the reaction of DPPH with Trolox. The importance of solvent acidity control in investigation of antioxidant properties is outlined.

Ecdysone agonists: mechanism and importance in controlling insect pests of agriculture and forestry.

Molting is the result of the expression of a cascade of genes that is sequentially both up and down-regulated by the molting hormone, 20-hydroxyecdysone (20E), which is secreted as a pulse during each instar. Benzoyl hydrazine analogs of 20E act like the native molting hormone at the molecular level by binding with the ecdysone receptor complex and transactivating a succession of molt initiating transcription factors that, in turn, induce the expression of a group of molt-related genes. As a result of the expression of these up-regulated genes, the larva undergoes apolysis and head capsule slippage and takes on the appearance of the pharate larva. However, unlike 20E, which is cleared at this juncture, allowing the down-regulated genes to be expressed, these synthetic analogs bind strongly to the receptors and remain in place and repress all the down-regulatory genes such as the ones necessary for cuticle elaboration, sclerotization, and ecdysis resulting in a developmental arrest in this state. As a result, the treated larva goes into a precocious incomplete molt that is lethal. Two of the analogs, tebufenozide and methoxyfenozide, are lepidopteran specific and have good control potential for open feeding larvae that ingest this material while a third one, halofenozide, acts on coleopteran larvae. Since they specifically act through an insect receptor complex, they have little or no effect on non-target species, making them environmentally attractive pest control agents. Some insects, however, show resistance to these analogs and this could be, inter alia, due to an ATP Binding Cassette Transporter like system that selectively pumps out the analogs.

Protectors of Oxidative Stress Inhibit AB(1-42) Aggregation in vitro

Department of Applied Chemistry and Recombinant Protein Expression Center, Sejong University, Seoul 143-747, Korea Received September 23, 2002Reactive oxygen species (ROS) have been investigated to have pivotal roles on amyloidogenecity of β-amyloidpeptide (Aβ), the major component of senile plaques in Alzheimer's disease (AD) brain. Addition of radicalscavengers is one of the on-going strategies for therapeutic treatment for AD patients. Hsp104 protein includingtwo ATP binding sites from Saccharomyces cerevisiae , as a molecular chaperone, was known to function as aprotector of ROS generation when exposed to oxidative stress in our previous study. This observation has ledus to investigate Hsp104 protein as a molecular mediator of A β aggregation in this study. We have developeda new way of expression for Hsp104 protein using GST-fusion tag. As we expected, formation of A β aggregatewas protected by wild type Hsp104 protein, but not by the two ATP-binding site mutant, based on Thioflavin-T fluorescence. Interestingly, Hsp104 protein was observed to keep A β from forming aggregates independentof ATP binding. On the other hand, disaggregation of Aβ aggregates by wild type Hsp104 was totallydependent on the presence of ATP. On the other hand, mutant Hsp104 with two ATP binding sites alteredexhibited no inhibition. Another effective antioxidant, hydrazine analogs of curcumin were also effective in A βfibrilization as protectors against oxidative stress. Based on these observations we conclude that Hsp104 andcurcumin derivatives, as protectors of oxidative stress, inhibit Aβ aggregation in vitro and can be candidatesfor therapeutic approaches in cure of some neurodegenerative diseases.Key Words : Hsp104, Antioxidants, Curcumin, Aβ aggregationIntroductionSeveral neurodegenerative diseases, such as Alzheimer’sDisease (AD), Parkinson Disease (PD) and Huntingtondisease (HD), result from accumulation of damaged proteinsinduced by oxidative stress.

Slow-binding inhibition of gamma-aminobutyric acid aminotransferase by hydrazine analogues.

(3-Hydroxybenzyl)hydrazine and methylhydrazine have been found to be potent slow-binding inhibitors of the pyridoxal 5-phosphate (PLP)-dependent enzyme gamma-aminobutyric acid aminotransferase (GABA-AT). Both compounds follow mechanism A (Morrison, J.F.; Walsh, C. T. Adv. Enzymol. 1988, 61, 201-301) which does not involve formation of a rapidly reversible enzyme-inhibitor complex before the formation of the final tight complex. The rate constant for formation of the enzyme-inhibitor complex determined from the slow-binding kinetics was 2.08 x 10(3) and 1.98 x 10(4) M-1 min-1 for methylhydrazine and (3-hydroxybenzyl)hydrazine, respectively. The rate constant for dissociation of the enzyme--inhibitor complex determined for the slow-binding kinetics was 4.6 x 10(-3) and 5 x 10(-3) min-1, respectively. The inhibition constants calculated from the slow-binding inhibition kinetics are 2.2 microM for methylhydrazine and 0.3 microM for (3-hydroxybenzyl)hydrazine. Reactivation of the inhibited enzyme was not first order, perhaps due to a side reaction of the hydrazine, but was consistent with the results obtained from the slow-binding kinetics. Inhibition constants were calculated from the level of enzyme activity at equilibrium inhibition. These constants are 2.8 and 0.46 microM for methylhydrazine and (3-hydroxybenzyl)hydrazine, respectively, in good agreement with those calculated from the slow-binding inhibition kinetics. 3-Hydrazinopropionate also behaved as a slow-binding inhibitor. However, the dependence of its kinetics on the concentration of inhibitor could not be described by the slow-binding or slow, tight-binding inhibition models. These kinetics could not be described by the tight-binding character of the inhibition because the addition of the competitive inhibitor propionic acid at 100 times its Ki did not affect the shape of the curve for inhibitor concentration dependence. The slow-binding inhibition appeared to require 2-4 molecules of 3-hydrazinopropionate/enzyme. The reactivation of enzyme inhibited by 3-hydrazinopropionate was first order with a rate constant of 6.9 x 10(-3) min-1. Its equilibrium inhibition constant was calculated to be < 20 nM. However, the inhibition constant calculated was dependent on the concentration of inhibitor because of the unusual character discussed above and may be much lower. Only 1 PLP/enzyme dimer reacted with methylhydrazine or (3-hydroxybenzyl)hydrazine, as indicated by Scatchard plots, or with 3-hydrazinopropionate, as shown by a spectrophotometric titration. Slow-binding inhibition does not appear to be the result of a significant enzyme conformational change because there is no change in the tryptophan fluorescence of GABA-AT upon binding either methylhydrazine or 3-hydrazinopropionate. Implications for the design of hydrazine inhibitors of GABA-AT are discussed.

Time-dependent inhibition of γ-aminobutyric acid aminotransferase, by 3-hydroxybenzylhydrazine

γ-Aminobutyric acid (GABA) aminotransferase is a pyridoxal 5′-phosphate (PLP)-dependent enzyme that catalyzes the conversion of GABA into succinic semialdehyde. Hydrazine analogues have long been known to act as inactivators of PLP-dependent enzymes, including GABA aminotransferase, however, no studies of the molecular mechanism of inactivation of PLP-dependent enzymes by hydrazines have been reported. 3-Hydroxybenzylhydrazine is shown to be a potent in vitro time-dependent inhibitor of pig brain GABA aminotransferase. UV-visible and 1H NMR studies, both with GABA aminotransferase and with PLP as a chemical model for the enzyme-catalyzed reaction, indicate that 3-hydroxybenzylhydrazine reacts both enzymatically and nonenzymatically to form the 3-hydroxybenzylhydrazone of PLP without tautomerization.

Deglycation of glycated proteins with hydrazine analogues

Glycated human serum albumin (glc HSA) and glc proteins in back hairs from diabetic rats were deglycated by incubation with hydrazine or aminoguanidine (guanylhydrazine) at physiological temperature (37°C). Glc HSA decreased by 35% with 0.2 M hydrazine at day 20 and by 56% with 0.1 M aminoguanidine at day 10. The glc proteins in hairs decreased by 40–50% and 70–77% with hydrazine and aminoguanidine at more than 0.1 M by day 20, respectively. The deglycation of glc protein with aminoguanidine was slower than that with hydrazine. The present result suggests that the inhibitory effects by aminoguanidine on the late Maillard reaction may include a decrease in the level of glc proteins (Amadori compounds) due to deglycation.

A comparative study of dimethylhydrazine regioisomers and the methylazoxymethanol metabolite of 1,1- and 1,2-dimethylhydrazine in relation to transformation in human fibroblasts

Comparative analysis of the cytotoxicity, transformation efficiency, induction of alkali labile sites (ALS) and DNA methylation in human foreskin fibroblasts was carried out with two dimethylhydrazine (DMH) regio-isomers (1,1-DMH and 1,2-DMH) and the acetate (A) derivative of the metabolite methylazoxymethanol (MAM) of 1,2-DMH. Effective ED 50 cytotoxic doses for MAMA, 1,1-DMH and 1,2-DMH were 0.056, 6.83 and 6.30 mM, respectively. MAMA and 1,1-DMH were more effective transformers than 1,2-DMH. However, methylation of purines accounted for less than 1% of the total radiolabel associated with DNA for all 3 agents. 1,2-DMH, 1,1-DMH and MAMA induced O 6MeGua/N 7MeGua ratio of 0.04, 0.32 and 0.18, respectively. Only MAMA induced measurable alkali labile lesions at transforming doses. These results suggest that other mechanisms may play a role in the initiation of transformation events by hydrazine analogues.

Purification and properties of a pyridoxal 5'-phosphate-dependent histidine decarboxylase from Morganella morganii AM-15.

A pyridoxal 5'-phosphate-dependent histidine decarboxylase from Morganella morganii AM-15 was purified to homogeneity. The enzyme is a tetramer (Mr 170,000) of identical subunits and binds 4 pyridoxal-P/tetramer; it is resolved by dialysis against cysteine at pH 6.8. Between pH 6.2 and 8.8, the holoenzyme shows pH-independent absorbance maxima at 333 and 416 nm. Vmax/Km is highest at pH 6.5; this optimum reflects chiefly increased Km values for histidine at lower or higher pH values, whereas Vmax is highest at pH 5.0 and decreases only moderately between pH 5.0 and 8.0. The enzyme also decarboxylates beta-(2-pyridyl)alanine and N tau-methylhistidine (but not N pi-methylhistidine); arginine, lysine, and ornithine are neither substrates nor inhibitors. The hydrazine analogue of histidine, 2-hydrazino-3-(4-imidazolyl)propionic acid, is a very potent competitive inhibitor; other carbonyl reagents and a variety of carboxyl- or amino-substituted histidines also inhibit competitively. alpha-Fluoromethylhistidine is a potent irreversible inhibitor of the enzyme; alpha-methylhistidine is a competitive inhibitor/substrate that is decarboxylated slowly and undergoes a slow decarboxylation-dependent transamination that converts the holoenzyme to pyridoxamine-P and apoenzyme. Dithiothreitol and other simple thiols are mixed-type inhibitors that interact with pyridoxal-P at the active site to form complexes (lambda max congruent to 340 nm), presumably the corresponding thioalkylamines, without resolving the holoenzyme. This histidine decarboxylase (Vmax = 72 mumol X min-1 X mg-1) is much more active than "homogeneous" preparations of mammalian pyridoxal-P-dependent histidine decarboxylase (Vmax congruent to 1.0) and is about equal in activity to the pyruvoyl-dependent histidine decarboxylases from Gram-positive bacteria.

1,2-diallylhydrazine dihydrochloride carcinogenesis in mice.

Continuous administration of 0.0625% 1,2-diallylhydrazine dihydrochloride in drinking water for life to 6-week-old randomly bred to Swiss mice induced lung tumors. In comparison with the untreated controls, the lung tumor incidence rose from 25 to 80% in the females and from 26 to 80% in the males. The treatment had no apparent effect on the development of other tumor types. Histopathologically, the lesions were classified as adenomas and adenocarcinomas of the lungs. The work is a continuation of our structure activity inquiry concerning the relative carcinogenic potencies of the dialkyl versus the monoalkyl series of hydrazine analogues.