Amino Acid Metabolism in Microorganisms

Certain strains of Streptomyces were found to convert l-methionine into 3-methylthio-propylamine (MTPA), but not d-methionine. Now, optical resolution of DL-methionine was attempted using this phenomenon. Streptomyces sp. K37 was cultured in a medium containing DL-methionine (10 mg/ml). The culture filtrate was applied to a column of Diaion SA-21A (OH form). MTPA was recovered from the effluent by ether exraction. The Diaion SA-21A was eluted with 1N HCl and the eluate was applied to a column of Diaion SK-1 (H form). d-Methionine was eluted from the column with 1N NH₄OH and recovered after concentration, decolorization with active carbon, and precipitation with ethanol. The yields of MTPA and d-methionine from the broth were 69.5% and 89.5%, respectively.     

Amino Acid Metabolism in Microorganisms

Certain Streptomyces strains were found to accumulate an unknown substance in culture broth when the microorganisms were grown in the medium containing dl-methionine. The substance was isolated from the culture broth as hydrochloride and was identified as 3-methylthiopropylamine (MTPA), decarboxylated product of methionine, from its melting point, chemical composition, infrared spectrum, and other properties. Cultural conditions for MTPA formation in Streptomyces sp. K 37 were investigated. The yield of MTPA from l-methionine reached about 90% with a culture medium containing corn steep liquor. Namely, 6.47 mg of MTPA per millilitre of culture broth was produced from 10 mg of l-methionine per millilitre of the growth medium. The transforming activity was found in the cells of the early culture period. MTPA-producing activity was induced by l- methionine in the medium. d-Methionine was not utilized as a substrate of the reaction with intact cells. Optimum pH for the reaction appeared to be 6.0~8.0.     

Metabolism of Aromatic Amino Acid in Microorganisms

Phenylalanine ammonia-lyase, which catalyzes the conversion of l-phenylalanine to trans-cinnamic acid and ammonia, has been partially purified from the cells of Rhodotorula. Some of the properties of this phenylalanine ammoyia-lyase were investigated. The enzyme was stable in phosphate buffer of pH over the range of 6.0 to 7.0 On heating, the enzyme was stable up to 50°C, but above 60°C, it was destroyed. The enzyme activity was strongly inhibited by p-chloromercuribenzoate at 10^?5 m and almost recovered by the addition of glutathione or mercaptoethanol at 10^?3 m. The present enzyme preparation of Rhodotorula also catalyzed the deamination of l-tyrosine to trans-p-coumaric acid. trans-p-Coumaric acid was isolated from the reaction mixture and identified by its absorption spectra. The rates of deamination showed optima at pH 9.0 and 9.5 for l-phenylalanine and l-tyrosine, respectively.     

Fatty Acid Metabolism in Microorganisms

The production of pimelic acid from azelaic acid by microorganisms was studied. About 100 strains of bacteria which were able to utilize azelaic acid as a sole carbon source were isolated from soil and other natural materials. Among these bacteria, several strains produced a large quantity of an organic acid (pimelic acid) from azelaic acid in their culture fluids during the cultivation. The acid was isolated from the culture fluid of strain A133 in crystalline form. The crystal was identified as pimelic acid by physicochemical and biological methods.

From the results of investigations on the morphological and physiological characters, the bacterial strain A133 was assumed to be Micrococcus sp.     

Fatty Acid Metabolism in Microorganisms

During the investigation on the metabolism of azelaic acid by Micrococcus sp., it was found that the bacterium produced a large amount of keto acid (α-ketoglutaric acid) under the restricted condition for nitrogen source. The acid was identified as α-ketoglutaric acid by physico-chemical and biological methods. The mechanism of the production of α-ketoglutaric acid from azelaic acid was investigated. From the result, it was suggested that α-ketoglutaric acid production proceeded thrpugh the further oxidation of acetic acid produced from azelaic acid and that the production might be functioned by TCA cycle enzymes of the bacterium. Similarly, α-ketoglutaric acid was found to be produced remarkably from other various fatty acids.     

Metabolism of Aromatic Amino Acids in Microorganisms

It was found that when Rhodotorula rubra IFO 0911 was grown in a phenylalanine medium, benzoic acid and p-hydroxybenzoic acid besides cinnamic acid were formed in the cultured both. The conversions of cinnamic acid into benzoic acid and of benzoic acid into p-hydroxybenzoic acid, and the degradation of p-hydroxybenzoic acid were demonstrated in intact cells of Rhodotorula rubra. These activities were observed in the cells grown on various media, including the medium containing no phenylalanine, and were found to be distributed widely in Rhodotorula. The cells of Rhodotorula rubra were also able to degrade p-coumaric acid, 3,4-dihydroxybenzoic acid (protocatechuic acid), p-hydroxyphenyl-acetic acid, 3-methoxy-4-hydroxycinnamic acid (ferulic acid) and 3-methoxy-4-hydroxybenzoic acid (vanillic acid). From these results, the metabolic pathways for phenylalanine and tyrosine in Rhodotorula were discussed.     

Anaerobic Amino Acid Metabolism

Anoxic stress induces a strong change in sugar, protein, and amino acid metabolism in higher plants. Sugars are rapidly consumed through the anaerobic glycolysis to sustain energy production. Protein degradation under anoxia is a mechanism to release free amino acids contributing in this way to maintaining the osmotic potential of the tissue under stress. Among free amino acids, a particular role is played by glutamic acid, being a precursor of some characteristic compounds of the anaerobic metabolism (alanine, -aminobutyric acid, and putrescine). The glutamine synthetase/glutamate synthase cycle contributes to ammonia reassimilation and primary assimilation of nitrate, and resynthesizes constantly glutamate for the synthesis of other compounds. Some polypeptides involved in these pathways are expressed under anoxia. The importance of amino acid metabolism for the response to anaerobic stress is discussed.     

胆汁酸代谢与肠道微生物

肠道微生物与胆汁酸代谢密切相关,肠道微生物参与了胆汁酸在肠道中的修饰过程;肠道微生物通过法尼醇受体影响胆汁酸的合成;肠道微生物通过调节胆汁酸的代谢影响机体健康,反过来胆汁酸也可以通过调节肠道微生物菌群的组成影响机体健康.肠道微生物与胆汁酸代谢间的稳态影响着机体健康,现对肠道微生物与胆汁酸代谢及其相互影响做一综述.     

Studies on Kojic Acid Metabolism by Microorganisms

An enzymatic oxidation of kojic acid to comenic aldehyde was found in the decomposition process of kojic acid by Arthrobacter ureafaciens strain (K-l), a kojic acid decomposing bacteria.

This enzyme was (probable a new type of non-heme iron protein) is assumed to catalyze the dehydrogenation of kojic acid, while the ferric ion contained in the enzyme is considered to serve as an acceptor of hydrogen released from kojic acid. The resulted ferrous ions are oxidized either by molecular oxygen under aerobic conditions or by NAD under anaerobic conditions, accompanying hydrogen peroxide in the former and reduced NAD in the latter. The enzyme was partially purified by using ammonium sulfate precipitation, gel filtration on Sephadex G-200 column and column chromatography with DEAE-Sephadex A-50. The activity increased to 85 fold, compared with crude extracts and the recovery of the activity was 33.9%. The optimum pH of the reaction was 7.75. The enzyme was inactivated by PCMB, and unstable upon heat treatment. A loss of about 50% of the activity was caused by heating at 35%C for 5 min, but some reducing agents protected the enzyme from PCMB inhibition and the heat inactivation. Not only kojic acid, but also benzyl kojic acid or 5-methoxy kojic acid may be substrates. Km value for kojic acid was 1.43 × 10^?5m. The molecular weight of the enzyme was estimated to be about 55,000 and the enzyme contained about two atoms of iron in one molecule. The reaction mechanism for kojic acid oxidase is discussed.     

Studies on Kojic Acid Metabolism by Microorganisms

An enzyme, comenic aldehyde dehydrogenase, which catalyzes the oxidation of comenic aldehyde to comenic acid was partially purified from cell extract of Arthrobacter ureafaciens K-1.

The enzyme was purified 31-fold at Sephadex G-100 filtration step, 112-fold at DEAE-Sephadex A-50 fractionation step, and recovery of the activity was 73.3% and 38.5% respectively.

NADP and magnesium ion were essential for the oxidation. The enzyme shows optimum activity at pH 7.8. Enzyme activity was extremely sensitive to sulfhydryl reagents such as p-chloromercuribenzoate and monoiodoacetate. l-Cysteine or dithiothreitol protected the enzyme from p-chloromercuribenzoate inhibition. Carbonyl reagents, such as hydroxylamine and semicarbazide, inhibit the enzyme reaction by formation of addition compounds between carbonyl reagents and aldehyde group of the substrate. The enzyme was completely inactivated after heating for 5 min at 40°C The Km for 5-methoxy comenic aldehyde is 2.5×10^?6 m, and for NADP is 0.4×1O^?6 m. The reaction product, 5-methoxy comenic acid was identified by paperchromatography. The characterization of the enzyme has been carried out by using 5-methoxy comenic aldehyde as the substrate in stead of comenic aldehyde.     

氨基酸代谢与肝性脑病

肝性脑病 (HepaticEncephalopathy)又称肝昏迷 ,即由于严重肝病引起的中枢神经系统功能紊乱 ,患者出现一系列神经精神病状 ,直至进入昏迷。在此仅从氨基酸代谢异常的角度叙述与肝性脑病的关系。     

Studies on the Metabolism of Pantothenic Acid in Microorganisms

The ability of the formation of coenzyme A from pantothenic acid and cysteine in the presence of AMP or ATP was searched in yeasts and bacteria. The result of screening showed that the activity was found in several yeasts and the bacteria belonging to the genera Sarcina, Corynebacterium and Brevibacterium. Particularly, Brevibacterium ammoniagenes IFO 12071 (ATCC 6871) accumulated a large amount of coenzyme A.

Isolation of the reaction products, which were synthesized by Brevibacterium ammoniagenes IFO 12071, were carried out. The isolates were identified as coenzyme A, dephosphocoenzyme A and phosphopantothenic acid.

The possibility for the formation of coenzyme A in a larger amount from pantothenic acid and cysteine was investigated with baker’s yeast under the condition coupled with ATP-generating system.

Effect of various factors affecting the accumulation of coenzyme A was investigated. Among them, glucose concentration and inorganic phosphorus concentration were the most important factors for its accumulation. Coenzyme A was not accumulated without the phosphorylation of AMP to ATP. Several cationic surfactants stimulated the accumulation of coenzyme A.

The amount of coenzyme A accumulated reached about 200 μg per ml of the reaction mixture under the suitable reaction conditions employed.     

Studies on the Metabolism of d-Amino Acid in Microorganisms

In the previous paper it was reported that a mold enzyme preparation from Aspergillus ustus strain f., which was found to oxidize d-glutamic acid specifically, was always accompanied by the oxidation of d-aspartic acid. The present study has been carried out to investigate whether or not d-glutamic and d-aspartic acids are oxidized by the same enzyme.

A highly purified enzyme preparation which still shows both activities has been obtained. Several evidences which support the assumption that the both reactions might be catalyzed by a single enzyme, which may be called d-monoamino-dicarboxylic acid oxidase, are also presented.     

Studies on the Metabolism of d-Amino Acid in Microorganisms

It is confirmed by a new method for the determination of d-glutamic acid, that Aerobacter strain A rapidly metabolizes d-glutamic acid, while it only shows feeble metabolic activity towards l-glutamic acid when it is grown on a dl-glutamate-K₂HPO₄ medium. A specific d-glutamic oxidase is demonstrated in the cell-free extracts of Aerobacter strain A. This enzyme seems to be different from d-glutamic-aspartic oxidase obtained from Aspergillus ustus by the authors, since the former has no activity towards d-aspartic acid.     

Studies on the Metabolism of Gallic Acid by Microorganisms

The intermediary metabolism of gallic acid by Aspergillus niger under the influence of some added inhibitors has been studied. The decomposition of gallic acid by lyophilized cells under fluoroacetate inhibition allowed cis-aconitic acid, α-ketoglutaric acid and citric acid to accumulate. A mechanism of gallic acid decomposition via cis-aconitic acid has been inferred.     

Decreases in Amino Acid and Acetylcholine Metabolism During Hypoxia

Abstract: Hypoxia impairs brain function by incompletely defined mechanisms. Mild hypoxia, which impairs memory and judgment, decreases acetylcholine (ACh) synthesis, but not the levels of ATP or the adenylate energy charge. However, the effects of mild hypoxia on the synthesis of the glucosederived amino acids [alanine, aspartate, γ-amino butyric acid (GABA), glutamate, glutamine, and serine] have not been characterized. Thus, we examined the incorporation of [U-¹⁴C]glucose into these amino acids and ACh during anemic hypoxia (injection of NaNO₂), hypoxic hypoxia (15 or 10% O₂), and hypoxic hypoxia plus hypercarbia (15 or 10% O₂ with 5% CO₂). In general, the synthesis of the amino acids and of ACh declined in parallel with each type of hypoxia we studied. For example, anemic hypoxia (75 mg/kg of NaNO₂) decreased the incorporation of [U-¹⁴C]glucose into the amino acids and into ACh similarly. [Percent inhibition: ACh (57.4), alanine (34.4), aspartate (49.2), GABA (61.9). glutamine (59.2), glutamate (51.0), and serine (36.7)]. A comparison of several levels (37.5, 75, 150, 225 mg/kg of NaNO₂) of anemic hypoxia showed a parallel decrease in the flux of glucose into ACh and into the amino acids whose synthesis depends on mitochondrial oxidation: GABA (r= 0.98), glutamate (r= 0.99), aspartate (r= 0.96), and glutamine (r= 0.97). The synthesis of the amino acids not dependent on mitochondrial oxidation did not correlate as well with changes in ACh metabolism: serine (r= 0.68) and alanine (r= 0.76). The decreases in glucose incorporation into ACh and into the amino acids with hypoxic hypoxia (15% or 10% O₂) or hypoxic hypoxia with 5% CO₂ were very similar to those with the two lowest levels of anemic hypoxia. Thus, any explanation of the brain's sensitivity to a decrease in oxygen availability must include the alterations in the metabolism of the amino acid neurotransmitters as well as ACh.