Amounts Of Tyrosine Research Articles

The effects of fermented pineapple residue on growth performance, meat quality, and rumen microbiota of fattening Simmental bull.

In this study, silage Pennisetum sinese Roxb-based diet was replaced with fermented pineapple residue (FPR) at the replacement ratio of 0% (CON), 25% (T25), and 50% (T50) in fattening Simmental bulls for 30 days to evaluate the effects of FPR on growth performance, serum indexes, and ruminal characteristics. A total of 30 Simmental bulls (546 ± 44 kg initial BW) were allocated to three groups according to a completely randomized design. On day 30, the slaughter performance and meat quality were determined. Rumen fluids were collected for analyzing the rumen fermentation parameters and microbiota composition on day 30. The results showed that the average daily weight gain increased (P < 0.05) as the proportion of FPR rose. Within treatments, the T25 group reached more profit (5.34 RMB per day per bull) than CON while T50 was 3.69. The content of crude fat, cysteine, and proline in the muscle of T50 increased significantly (P < 0.05). The amounts of tyrosine, proline, and phenylalanine were significantly increased in the T25 (P < 0.05). The beta diversity analysis showed significant differences among the rumen bacterial flora of each group (P < 0.05). In the T25 group, the relative abundance of Spirochaetes decreased significantly (P < 0.05). The relative abundance of Lachnospiraceae_bacterium_RM44 was significantly lower (P < 0.05). Thus, FPR could improve the growth performance, economic benefits, and meat quality without adverse effects on ruminal characteristics.

Isolation, Screening, and Identification of Proteolytic Lactic Acid Bacteria from Indigenous Chao Product

ABSTRACTThe aim of the study was to isolate, select, and identify proteolytic lactic acid bacteria (LAB) from chao, a traditional fermented fish from Pangkajene and Kepulauan Regency, South Sulawesi, Indonesia. LAB was isolated by poured plate method. Proteolytic LAB were selected using agar skim milk media. Protease activity of LAB was determined based on the amount of tyrosine released in unit/mL. Proteolytic LAB were identified using API 50 CHL kit and 16S rRNA gene sequence analysis. The result showed that a total of 60 isolates were obtained from chao, and 57% of them were cocci-shape. Fifteen isolates were halotolerant proteolytic LAB. Their R values and protease activity were 2.11–3.39 and 0.267–0.304 U/mL, respectively. Identification by API 50 CHL kit showed that four rod-shape isolates were Lactobacillus plantarum, and two others were Lactobacillus curvatus. Cocci-shape isolates could not be identified as cocci bacterium. Rep-PCR results showed that there were two kinds of bands, namely thick and thin. Two isolates were selected from two types of bands that had the highest R for the analysis of 16S rRNA gene sequences, namely Ags1-3 and Ags7-3. The results showed that Ags1-3 isolate was identified as Lactobacillus plantarum and Ags7-3 as Pediococcus acidilactici.

The study of lentil flour as a raw material for production of semi­smoked sausages

In the production of sausages, soy and products of its processing, varieties of food soy flour are mainly used as an additional component. It has been established in a study of safety of using soy that a large number of genetically modified organisms used as foodstuffs have appeared in recent years. The possibility of using peas, beans, lentils and chickpeas would ensure enrichment of products with high­quality food protein easily absorbed by human organism. Lentil is rich in free amino acids, it contains glutamic and aspartic acids and a large amount of tyrosine. The study has substantiated technological parameters of lentil sprouting, the degree of grinding of lentil flour was established, influence of sprouting on changes in the lentil amino acid composition was revealed, level of assimilability of lentil protein and the redundancy factor were studied. The studies were conducted with lentil grains. Sprouting was carried out in a special tank of a round shape which included a grid. A hole in the bottom of the tank was provided for water drainage. The water tank was placed under the grates and filled with water to soak lentil for 8 hours at 17±2 °C until 1 cm long sprouts were formed. Lentil grains were ground using laboratory mills to a particle size of 1...1.5 mm and 0.2...0.4 mm. It was established that the use of lentil flour with a particle size of 0.2...0.4 mm has resulted in improvement of technological properties of minced meat: an increase in the amount of bound moisture to 83.25 % ensuring plasticity of minced meat of 7.81 cm 2 /g. All of this contributed to intensification of osmotic processes in minced meat. For disinfection of microflora and to ensure compliance of products with sanitary requirements, a microwave dryer was used. Its operation time consisted of 6 cycles by 6 minutes each for operation of the modules and 7 minutes for switching off the modules. It was found by the results of the study of amino acid composition that sprouting affected growth of the share of essential amino acids 15 % better compared to non­sprouted lentil flour. The protein assimilability of sprouted lentil was 62.91 % and the redundancy coefficient was 21.25 % which enables its use in the technology of semi­smoked sausages. It has been established that the use of sprouted lentil flour improved the coefficient of efficiency of protein use by the organism by an average of 30 %

Metabolite Profiling during Fermentation of Makgeolli by the Wild Yeast Strain Saccharomyces cerevisiae Y98-5

Makgeolli is a traditional Korean alcoholic beverage. The flavor of makgeolli is primarily determined by metabolic products such as free sugars, amino acids, organic acids, and aromatic compounds, which are produced during the fermentation of raw materials by molds and yeasts present in nuruk, a Korean fermentation starter. In this study, makgeolli was brewed using the wild yeast strain Saccharomyces cerevisiae Y98-5, and temporal changes in the metabolites during fermentation were analyzed by ultra-high-performance liquid chromatography-quadrupole-time-of-flight mass spectrometry. The resultant data were analyzed by partial least squares-discriminant analysis (PLS-DA). Various metabolites, including amino acids, organic acids, sugar alcohols, small peptides, and nucleosides, were obviously altered by increasing the fermentation period. Changes in these metabolites allowed us to distinguish among makgeolli samples with different fermentation periods (1, 2, 3, 6, 7, and 8 days) on a PLS-DA score plot. In the makgeolli brewed in this study, the amounts of tyrosine (463.13 μg/mL) and leucine (362.77 μg/mL) were high. Therefore, our results indicate that monitoring the changes in metabolites during makgeolli fermentation might be important for brewing makgeolli with good nutritional quality.

The relationship between consumption of tyrosine and phenylalanine as precursors of catecholamine at breakfast and the circadian typology and mental health in Japanese infants aged 2 to 5 years

BackgroundThis study aims to examine the relationship between tyrosine and phenylalanine intake at breakfast as precursors of dopamine, and scores on the Torsvall-Åkerstedt Diurnal Type Scale and of mental health in Japanese infants aged 2 to 5 years.ResultsAn integrated questionnaire was administered to parents of 1,367 infants attending one of ten nursery schools governed by Kochi City or a kindergarten affiliated with the Faculty of Education at Kochi University (775 answers for analysis: 56.7%) in May and June 2008. Questionnaires included the Torsvall-Åkerstedt Diurnal Type Scale and questions on sleep habits (onset, offset, quality, quantity, and so on), meal habits (content and regularity of timing), and mental health (depressive states). Amount of tyrosine and phenylalanine intake was calculated based on a breakfast content questionnaire and data on the components of amino acids in foods. Infants who ingested more than 800 mg of tyrosine or phenylalanine at breakfast per meal were more morning-type than those who ingested less than 800 mg (ANOVA: P= 0.005). However, this relationship disappeared in the ANCOVA analysis (with the covariance of tryptophan intake, P= 0.894). Infants who ingested more than 800 mg of the two amino acids at breakfast showed significantly higher mental health scores (lower frequency of depressive states) than those who ingested less than 800 mg (ANOVA: P = 0.004). This relationship remained significant when ANCOVA analysis was performed with the covariance of tryptophan (ANCOVA: P= 0.017).ConclusionsThese results suggest that tyrosine and phenylalanine ingested at breakfast are not related with circadian phase, but are relate with mental health in infants.

Effect of Application of Nitrogen and Different Nitrogen–Sulfur Ratios on the Quality and Quantity of Mustard Seed

A greenhouse experiment was conducted on a calcareous chernozem soil to investigate the effects of nitrogen (N) and sulfur (S) fertilization and their ratios on the yield and quality of white mustard (Sinapis alba L.). Four levels of N [0.5, 1, 1.5, and 2 g pot−1 N as ammonium nitrate (NH4NO3) and ammonium phosphate (NH4H2PO4)] in combination with three levels of applied N–S ratios [8, 4, 2; S as potassium sulfate (K2SO4) and sodium sulphate (Na2SO4)] were tested as treatments. Results indicated that a significant response to seed yield was observed for N and S application. Maximum yield, 24.8 g pot−1, was found when full doses of N and S were applied. Increasing N supply from 0.5 g pot−1 to 1 g pot−1 had little increasing effect in the oil content of the seed. Higher application of N doses (>1 g pot−1) decreased these values significantly. The maximum oil content (28%) was achieved with the 1 g N pot−1 treatment; the lowest values were observed in the pots applied with the highest N doses. Changes in the N content of the seed and straw showed a statistically significant increase with increasing N and S fertilization. Highest values in the seed and straw (5.96% and 0.87%, respectively) were observed by applying highest N and S doses. Seed and straw S levels were also observed to increase with increasing N rates and decreasing N–S ratio. Nitrogen doses significantly improved the quantities of essential amino acids with the exception of threonine, tyrosine, phenylalanine, and methionine. The amounts of these amino acids decreased with increasing N supply. When the N–S ratio decreased by increasing S, the quantities of valine, isoleucine, leucine, lysine, methionine, and cysteine increased significantly and the amount of tyrosine decreased. The quantities of nonessential amino acids with the exception of proline, histidine, and glycine increased with increasing N doses. In contrast, N rates decreased the amount of glycine. Decreasing the N–S ratio lowered the proline and arginine contents. The total amounts of essential amino acids slightly increased with increasing N rates and decreasing N–S ratio.

Sigma's Non-specific Protease Activity Assay - Casein as a Substrate

Proteases break peptide bonds. In the lab, it is often necessary to measure and/or compare the activity of proteases. Sigma's non-specific protease activity assay may be used as a standardized procedure to determine the activity of proteases, which is what we do during our quality control procedures. In this assay, casein acts as a substrate. When the protease we are testing digests casein, the amino acid tyrosine is liberated along with other amino acids and peptide fragments. Folin and Ciocalteus Phenol, or Folin's reagent primarily reacts with free tyrosine to produce a blue colored chromophore, which is quantifiable and measured as an absorbance value on the spectrophotometer. The more tyrosine that is released from casein, the more the chromophores are generated and the stronger the activity of the protease. Absorbance values generated by the activity of the protease are compared to a standard curve, which is generated by reacting known quantities of tyrosine with the F-C reagent to correlate changes in absorbance with the amount of tyrosine in micromoles. From the standard curve the activity of protease samples can be determined in terms of Units, which is the amount in micromoles of tyrosine equivalents released from casein per minute.To view this article in Chinese, click here

Sigma's Non-specific Protease Activity Assay - Casein as a Substrate

Proteases break peptide bonds. In the lab, it is often necessary to measure and/or compare the activity of proteases. Sigma's non-specific protease activity assay may be used as a standardized procedure to determine the activity of proteases, which is what we do during our quality control procedures. In this assay, casein acts as a substrate. When the protease we are testing digests casein, the amino acid tyrosine is liberated along with other amino acids and peptide fragments. Folin and Ciocalteus Phenol, or Folin's reagent primarily reacts with free tyrosine to produce a blue colored chromophore, which is quantifiable and measured as an absorbance value on the spectrophotometer. The more tyrosine that is released from casein, the more the chromophores are generated and the stronger the activity of the protease. Absorbance values generated by the activity of the protease are compared to a standard curve, which is generated by reacting known quantities of tyrosine with the F-C reagent to correlate changes in absorbance with the amount of tyrosine in micromoles. From the standard curve the activity of protease samples can be determined in terms of Units, which is the amount in micromoles of tyrosine equivalents released from casein per minute. To view this article in Chinese, click here

Studies on a new dinuclear CoII–pterin complex exhibiting reactivity towards phenylalanine and bromobenzene

2-Pivaloylamino-6-acetonyl-isoxanthopterin (1, \({\hbox{H}_{2}\hbox{L}}\)) has been reacted with \({\hbox{CoCl}_{2}\cdot 6\hbox{H}_{2}\hbox{O}}\) under suitable conditions for synthesizing the new compound \({\hbox{Na}[\hbox{Co}_{2}^{\rm II}\hbox{(L)}\hbox{Cl}_{3}(\hbox{CH}_{3}\hbox{OH})_{3}}\)] (2). It has been characterized by elemental analysis, electrospray ionization mass spectrometry, magnetic susceptibility measurement, different spectroscopic techniques, and cyclic voltammetry. Molecular mechanics (MM2) method provided with its optimized geometry (having lowest steric energy), consistent with the above data; the optimized bond lengths and bond angles data tally with the literature X-ray structural data. Reactivity of (2) towards phenylalanine in the presence of \({\hbox{O}_{2}}\) in methanol has been followed both kinetically and stoichiometrically; a reasonable amount of tyrosine could be recovered from the reaction medium. The negative \({\Delta\hbox{S}^{\#}}\) value (−274.0 J mol−1\({\hbox{deg}^{-1})}\) indicates an associative pathway for this process. (2) is also able to react with bromobenzene as indicated by time-dependent absorption spectra as well as product identification. Efficacy of the pterin ligand residue \({(\hbox{L}^{2-})}\) of (2) in rendering the latter reactive towards the above-mentioned organic compounds, has been discussed on the basis of experimental evidence.

The Secreted Pyomelanin Pigment of Legionella pneumophila Confers Ferric Reductase Activity

The virulence of Legionella pneumophila is dependent upon its capacity to acquire iron. To identify genes involved in expression of its siderophore, we screened a mutagenized population of L. pneumophila for strains that were no longer able to rescue the growth of a ferrous transport mutant. However, an unusual mutant was obtained that displayed a strong inhibitory effect on the feoB mutant. Due to an insertion in hmgA that encodes homogentisate 1,2-dioxygenase, the mutant secreted increased levels of pyomelanin, the L. pneumophila pigment that is derived from secreted homogentisic acid (HGA). Thus, we hypothesized that L. pneumophila-secreted HGA-melanin has intrinsic ferric reductase activity, converting Fe(3+) to Fe(2+), but that hyperpigmentation results in excessive reduction of iron that can, in the case of the feoB mutant, be inhibitory to growth. In support of this hypothesis, we demonstrated, for the first time, that wild-type L. pneumophila secretes ferric reductase activity. Moreover, whereas the hyperpigmented mutant had increased secreted activity, an lly mutant specifically impaired for pigment production lacked the activity. Compatible with the nature of HGA-melanins, the secreted ferric reductase activity was positively influenced by the amount of tyrosine in the growth medium, resistant to protease, acid precipitable, and heterogeneous in size. Together, these data represent the first demonstration of pyomelanin-mediated ferric reduction by a pathogenic bacterium.

Effect of tyrosine on tyramine formation during beer fermentation

Changes in tyramine, in its precursor amino acid tyrosine, and in Pediococcus spp. were followed during 54 beer fermentations. No statistical relationship between tyramine production and wort tyrosine levels was found, either between the amount of tyramine formed or the decrease in tyrosine through beer fermentation. However, tyramine formation significantly correlated with Pediococcus spp. contamination (r=0.876; P<0.001, n=54). Higher initial tyrosine levels did not induce greater tyramine formation when a similar degree of contamination by Pediococcus spp. occurred, either between tyrosine decrease and tyramine formation. Special attention is required in controlling the presence of lactic acid bacteria to minimise the formation of tyramine. However, the amount of tyrosine does not seem to be a critical factor in the tyramine formation during beer fermentation.

Pterin-6-aldehyde, Xanthine Oxidase Inhibitor and Superoxide Scavenger, Directly React with Peroxynitrite

The effect of pterin-6-aldehyde (P6A), xanthine oxidase inhibitor and superoxide scavenger, on the production of nitrotyrosine as a footprint of tyrosine nitration by peroxynitrite, was compared with that of uric acid, a peroxynitrite scavenger. The amounts of tyrosine, P6A and nitrotyrosine were quantified using reversed-phase high-performance liquid chromato-graphy (RP-HPLC). P6A suppressed nitrotyrosine formation less effectively than uric acid, that is, 0.25 mM P6A reduced nitrotyrosine formation to 67.9± 10.8%, while 0.025 mM uric acid reduced it to 34.2± 1.6%. In living systems, peroxynitrite is generated by the reaction of super-oxide with nitric oxide and has a variety of toxic effects. Our results show that P6A is not necessarily a strong scavenger of peroxynitrite. However, since P6A is a potent scavenger of superoxide, P6A is thought to totally suppress peroxynitrite generation. Compounds that scavenge both superoxide and peroxynitrite may be useful in tissue damage in which reactive oxygen species are involved.

The losses of nutrients during the production of strained (Torba) yoghurt

Abstract A traditional method has been used in the production of Torba yoghurt (a strained yoghurt produced from cow’s, goat’s or sheep’s milk) and this is based on straining with a special cloth bag. In this study, the losses of nutrients during the straining of yoghurt were as follows: 51.8% thiamin, 60.5% riboflavin, 7.28% protein, 0.77% fat, 71.1% lactose, 70.2% sodium, 68.2% potassium, 65.6% calcium and 50.2% phosphorus. Among the amino acids the least loss occurred in the amount of tyrosine (2.24%) and the loss of histidine was highest (11.4%).

Purification and characterization of a male-specific protein in the hemolymph of the wax moth, Galleria mellonella L.

A male-specific protein (MSP) present only in males was identified from the hemolymph of the wax moth, Galleria mellonella L., by polyacrylamide gel electrophoresis (PAGE) and purified by anion-exchange chromatography. MSP has a native molecular mass of 55 kDa and consists of two 27-kDa subunits. An isoelectric point of MSP was measured to be approximately 5.8. MSP is a glycoprotein that contains 1.7% carbohydrate. The compositional analysis of carbohydrate component indicated a predominance of fructose and glucose. MSP also contains large amounts of asparagine, aspartic acid, glutamine, glutamic acid, and lysine but small amounts of tyrosine, methionine, and tryptophan. Western blot analysis of the hemolymph of each developmental stage indicated that MSP is present in the hemolymph of 8-day-old pupa and adult. Also, results from Western blotting indicated that MSP is not present in the tissues of larvae and of female adults but appears in the fat body of male pupae and adult and testis of adult. The fat body and testis of male pupae and adult were cultured in vitro to trace the place and time of MSP synthesis. The fat body began to synthesize MSP in late pupae and showed active synthesis during the adult stage. The distribution of MSP in the testis was observed by electron microscopic immunogold labeling, using the antibody against MSP. MSP is present between the germinal cysts and is taken up through the basal surface of the seminiferous tubular epithelium.

The anticonvulsant effect of citalopram on El mice, and the levels of tryptophan and tyrosine and their metabolites in the brain.

Serotonin(5-HT) plays an important role in the seizures of El mice since the seizure threshold of El mice correlates with the 5-HT concentration in the central nervous system. In this study, the anticonvulsant effect of a 5-HT reuptake blocker, citalopram, was evaluated behaviorally and biochemically. El mouse convulsions were inhibited by oral administration of citalopram for 2 weeks. Citalopram increased tryptophan and tyrosine amounts, and decreased the 5-HT, 5-hydroxyindoleacetic acid, kynurenine, and dopamine amounts in the brain. These findings show that citalopram depresses monoaminergic metabolism. Given the known convulsant effect of kynurenine, it is suggested that its decrease by citalopram may involve attenuation of El mice seizures.

Modulation of Peroxidation in Murine Melanoma by Dietary Tyrosine-Phenylalanine Restriction, Levodopa Methylester Chemotherapy, and Sodium Ascorbate Supplementation&lt;xref ref-type="fn" rid="FN2"&gt;2&lt;/xref&gt;

Treatment with the drug combination of levodopa methylester and benserazide, supplemental ascorbate, and dietary deficiencies of tyrosine and phenylalanine more than doubled the median survival time of female (C57BL/6 X DBA/2)F1 mice bearing B16 melanoma tumors. The mechanism for this antitumor effect was not well defined. This study was designed to test the hypothesis that the antitumor activity of levodopa methylester and ascorbate against B16 melanoma is related to the generation of free radicals of oxygen, which peroxidize lipid constituents of cell membranes leading to cell death. As an indication of lipid peroxidation, the individual and combined effects of drug treatment and ascorbate supplementation on host and tumor malondialdehyde levels were examined in mice fed one of three test diets (commercial, purified, or deficient) containing decreasing amounts of tyrosine and phenylalanine. Malondialdehyde levels were increased in the livers of all untreated tumor-bearing mice, which suggests that the tumor alters host antioxidant defenses. Drug treatment and ascorbate supplementation alone and in combination increased hepatic malondialdehyde levels inversely to the amounts of tyrosine and phenylalanine in the diet, and the effects of drug and ascorbate on malondialdehyde levels were additive. Plasma levels remained unchanged by drug treatment, ascorbate supplementation, or tumors in mice fed the commercial or purified diets. Higher levels were observed only in tumor-bearing mice fed the deficient diet and given both drug treatment and ascorbate supplementation. Changes in tumor malondialdehyde levels generally correlated with the effects of the drug and ascorbate on survival time of mice bearing B16 melanoma. Tumors from mice fed the commercial diet accumulated little malondialdehyde, and therapy was relatively ineffective in this dietary group. In mice fed purified or deficient diets, drug treatment and ascorbate supplementation alone increased survival and tumor malondialdehyde levels, but the level of peroxidation in mice receiving the ascorbate supplementation was low compared to its greater antitumor effect on B16 melanoma. Although ascorbate enhanced the peroxidative activity of the drug on B16 melanoma tumors, the effects of the drug and ascorbate on malondialdehyde levels were not additive. Ascorbate enhanced survival of tumor-bearing mice that were fed the deficient diet and that were treated with drug, which indicated that ascorbate supplementation acted via other mechanisms.(ABSTRACT TRUNCATED AT 400 WORDS)

Availability of phenylalanine and tyrosine for brain norepinephrine synthesis in developmentally protein-malnourished rats

Ontogenetic changes in brain phenylalanine, tyrosine, and norepinephrine concentrations occurred in rats as sequelae of protein inadequacies incurred during prenatal and postnatal development. The malnourished pups, whose dams received a low protein diet (8% casein) starting 5 weeks prior to conception, showed significantly elevated brain phenylalanine and norepinephrine, but not tyrosine, at most ages examined compared with offspring from dams fed a normal diet (25% casein) throughout the same time interval. Although the brain tyrosine concentrations of the malnourished offspring were somewhat lower than the normal pups, these decreases were found only at some ages and were restricted to certain brain regions (mainly the telencephalon and the cerebellum). Also, the peripheral availabilities of phenylalanine and tyrosine in the protein-deprived rats during the study (birth to age 30 days) displayed alterations which corresponded to their brain concentrations of these amino acids (increases of the former and decreases of the latter versus the controls). Although the malnourished rats had lower plasma tyrosine concentrations than the normal pups, both groups of offspring consistently showed higher concentrations of this amino acid compared with their phenylalanine values throughout postnatal development. In the case of the deprived rats, the increased availability of the semiessential rather than the essential amino acid to their brains may explain, in part, why the amounts of tyrosine in their brain-stem regions were generally comparable to the normal animals. This, in turn, may indirectly account for the higher amine biosynthesis in the brains of the malnourished pups. Overall, the present data demonstrate that the nutritional status with respect to the amount of dietary protein during prepartum and postpartum development has an important role in determining the substrate availability of tyrosine and/or phenylalanine for brain norepinephrine metabolism.

Vakaleris-Price and Hull Methods for Determining Soluble Tyrosine and Tryptophan in Blue Cheese

To establish a suitable method for measuring the degree of proteolysis in blue cheese (as a measure of ripening), the Hull procedure and the Vakalaris-Price method were compared. In recovery experiments using three different spectrophotometers and known amounts of tyrosine and tryptophan, discrepancies between the three spectrophotometers in their absorbance readings at 290nm were wide. To eliminate discrepancies that could have been caused by differing sensitivities of instruments, we used a wavelength of 285nm instead of 290nm.Seven loaves of domestic blue cheese were examined. High tyrosine contents were obtained in five of seven blue cheese samples with the Vakalaris-Price method as compared with Hull procedure. Extracts from blue cheese contained interfering compounds that absorbed at the ultraviolet-wavelength used with the Vakalaris-Price procedure.

Changes in chemical composition of anterior lens capsules of cataractous human eyes as a function of age

Amino acids and carbohydrates were found to account for 80% and 11%, respectively, of the dry weight of the anterior lens capsule of the cataractous human lens. The human lens capsule was found to contain substantial amounts of glycine, hydroxyproline, proline and glycosylated hydroxylysine, as is typical of basement membranes. The monosaccharides present in the lens capsule were identified as glucose, galactose, fucose, mannose, glucosamine, galactosamine and sialic acid. In contrast with basement membranes studied so far, hydroxylysine in human anterior lens capsules from cataractous lenses is almost completely glycosylated. Lenses used in this study were divided into two age groups: ≤ 65 years and &> 65 years. There were statistically significant differences between capsules from the two groups. In the older group, amounts of tyrosine, phenylalanine, histidine, lysine, and arginine were significantly higher and hydroxyproline was significantly lower. These compositional differences are consistent with a smaller proportion of collagen in the older age group.

Lethality of tyrosine in mice

High doses of tyrosine were found to be lethal in mice. The lethality was potentiated by decarboxylase inhibitors which acted by elevating tissues tyrosine levels when given together with large amounts of tyrosine. The lethality of either tyrosine or tyrosine given in combination with decarboxylase inhibitors was found to be correlated with the elevation of tyrosine levels in liver. This toxicity does not appear to involve either tyramine or p-hydroxyphenylpyruvic acid formation. Ascorbic acid pretreatment afforded a marked protection against tyrosine toxicity. This compound was found to prevent the elevation of tissue tyrosine levels by stimulating p-hydroxyphenylpyruvic acid oxidase, increasing the urinary excretion and inhibiting the gastrointestinal absorption of tyrosine.