Syntheses of L-tyrosine-related amino acids by tyrosine phenol-lyase of Citrobacter intermedius

Degradation of tyrosine to phenol, pyruvate and ammonia by tyrosine phenol-lyase from Citrobacter intermedius (formerly named Escherichia intermedia) is readily reversible at high concentrations of pyruvate and ammonia. Spectrophotometric studies indicate that ammonia is the first substrate which interacts with bound pyridoxal 5'-phosphate. Kinetic results show that pyruvate is the second substrate bound, hence phenol must be the third. When an appropriate phenol derivative is substituted for phenol, the corresponding tyrosine analogue can be synthesized. 3-Fluoro-, 2-fluoro-, 3-chloro-, 2-chloro-, 3-bromo-, 2-bromo-, 2-iodo-, 3-methyl-, 2-methyl- and 2-methoxy-L-tyrosines have been synthesized by this reaction. By using various phenol derivatives or tyrosine analogues as substrates, the substrate specificity of tyrosine phenol-lyase is investigated and the situation of its active site is discussed.

Purification and characterization of polyethylene glycol dehydrogenase involved in the bacterial metabolism of polyethylene glycol

Polyethylene glycol (PEG) dehydrogenase in crude extracts of a PEG 20,000-utilizing mixed culture was purified 24 times by precipitation with ammonium sulfate, solubilization with laurylbetaine, and chromatography with diethylamino-ethyl-cellulose, hydroxylapatite, and Sephadex G-200. The purified enzyme was confirmed to be homogeneous by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The molecular weight of the enzyme, which appeared to consist of four identical subunits, was 2.4 X 10(5). The enzyme was stable below 35 degrees C and in the pH range of 7.5 to 9.0. The optimum pH and temperature of the activity were around 8.0 and 60 degrees C, respectively. The enzyme did not require any metal ions for activity and oxidized various kinds of PEGs, among which PEG 6,000 was the most active substrate. The apparent Km values for tetraethylene glycol and PEG 6,000 were about 10.0 and 3.0 mM, respectively.

Purificaton and characterization of S-formylglutathione hydrolase from a methanol-utilizing yeast, Kloeckera sp. No. 2201

S-Fromylglutathione hydrolase (EC 3.1.2.12), a glutathione thiol esterase, was purified from a methanol-utilizing yeast, Kloeckera sp. No. 2201, to homogeneity as judged by polyacrylamide gel electrophoresis. The molecular weight of the native enzyme was determined to be 58 000 by gel filtration. The enzyme appeared to be composed of two identical subunits (Mr = 31 000). The apparent Km for S-formylglutathione was 0.077 mM. The optimum temperature was 50 degrees C and the optimum pH was 6.4-6.6. The enzyme was inhibited by several types of sulfhydryl reagents. The purified enzyme preparation contained no activity of formaldehyde dehydrogenase or of formate dehydrogenase. It is thought that three enzymes, formaldehyde dehydrogenase, S-formylglutathione hydrolase and formate dehydrogenase, participate in the oxidation of formaldehyde to CO2 in Kloeckera sp. No. 2201.

Total lung ectoplasia with systemic arterial supply

A 6-month-old girl was not to have fever and stridor. Investigations revealed an abnormal lung that communicated with the esophagus and had a systemic arterial supply from the abdominal aorta. Resection of the abnormal lung was performed successfully. We have termed this disorder total lung ectoplasia. Ten patients from the literature were reviewed.

Acceleration of methaemoglobin reduction by riboflavin in human erythrocytes

The effect of riboflavin on nitrite treated erythrocytes from normal subjects and patients with hereditary methaemoglobinaemia due to the deficiency of NADH-cytochrome b5 reductase was studied in the presence of glucose, 2-deoxy-D-glucose or lactate. When glucose or 2-deoxy-D-glucose was used as a substrate for these erythrocytes, the rate of methaemoglobin reduction in these cells was accelerated more than two-fold in the presence of riboflavin. The acceleration was dependent on the concentration of riboflavin and was suppressed by the addition of atebrin. The stimulative effect of riboflavin was, however, not observed when lactate was used in place of glucose or 2-deoxy-D-glucose. On the basis of these results, the acceleration of methaemoglobin reduction by riboflavin was considered to be due to the activation of NADPH-flavin reductase (Yubisui et al, 1977) in erythrocytes by the reagent. The availability of riboflavin for patients with methaemoglobinaemia due to the deficiency of NADH-cytochrome b5 reductase and for those with toxic methaemoglobinaemia is discussed in relation to methaemoglobin reducing systems in erythrocytes.

Bacterial oxidation of polyethylene glycol

The metabolism of polyethylene glycol (PEG) was investigated with a synergistic, mixed culture of Flavobacterium and Pseudomonas species, which are individually unable to utilize PEGs. The PEG dehydrogenase linked with 2,6-dichlorophenolindophenol was found in the particulate fraction of sonic extracts and catalyzed the formation of a 2,4-dinitrophenylhydrazine-positive compound, possibly an an aldehyde. The enzyme has a wide substrate specificity towards PEGs: from diethylene glycol to PEG 20,000 Km values for tetraethylene glycol (TEG), PEG 400, and PEG 6,000 were 11, 1.7, and 15 mM, respectively. The metabolic products formed from TEG by intact cells were isolated and identified by combined gas chromatography-mass spectrometry as triethylene glycol and TEG-monocarboxylic acid plus small amounts of TEG-dicarboxylic acid, diethylene glycol, and ethylene glycol. From these enzymatic and analytical data, the following metabolic pathway was proposed for PEG: HO(CH2CH2O)nCH2CH2OH leads to HO(CH2CH2O)nCH2CHO leads to HO(CH2CH2O)nCH2COOH leads to HO(CH2CH2O)n-1CH2CH2OH.

3-Hexulosephosphate synthase from Methylomonas aminofaciens 77a. Purification, properties and kinetics

3-Hexulosephosphate synthase (D-arabino-3-hexulose 6-phosphate formaldehyde lyase) was purified from an obligate methylotroph, Methylomonas aminofaciens, to homogeneity as judged by polyacrylamide gel electrophoresis and analytical ultracentrifugation. The molecular weight was determined to be 45 000-47 000 by sedimentation velocity and gel filtration. The enzyme appears to be composed of two identical subunits (Mr = 23 000). A bivalent cation is required for the activation and stabilization of the enzyme. The enzyme is specific for formaldehyde and D-ribulose 5-phosphate. The optimum pH is 8.0 (isoelectric point, pH 5.1) and the optimum temperature is 45 degrees C. Initial velocity studies are consistent with a sequential mechanism. The Michaelis constants are 0.29 mM for formaldehyde and 0.059 mM for D-ribulose 5-phosphate.

Vitamin B6 biosynthesis and nucleoside effect in the resting cell system of Flavobacterium sp. 238-7

As one of the attempts to find clues on precursors or intermediates of the vitamin B6 biosynthetic pathway, the resting cell system of Flavobacterium sp. 238-7, a bacterium producing a high amount of the vitamin, was employed. Among various compounds tested as an additive to the reaction mixture, L-glutamate and nucleoside derivatives increased the formation of vitamin B6, respectively. The possible mechanism of the participation of these compounds in vitamin B6 biosynthesis is discussed. The identification of vitamin B6 formed in the reaction mixture was done using column chromatography.

Action of 5-(2-thienyl)valeric acid as a biotin antagonist

5-(2-Thienyl)valeric acid (TVA), a biotin analogue which can be easily prepared through chemical process, inhibited the growth of a biotin synthesizing Rhodotorula glutinis. The growth inhibition was reversed by the addition of biotin. Among biotin intermediates, dethiobiotin and 7,8-diaminopelargonic acid reversed the inhibition by TVA, while 7-keto-8-amino-pelargonic acid and pimelic acid did not. From these results, it was concluded that TVA is a biotin antagonist which probably acts as an inhibitor of biotin biosynthesis.

Dependency representing Markov properties of spike trains recorded from central single neurons

Neuronal spike trains are regarded as stochastic point processes. To estimate the order and the vale of Markov properties of the adjacent interspike interval sequences, we have proposed new statistics "dependency" Dm for discrete variable and "simplified dependency" Dm for continuous variable in the stationary point processes, and Dm(t) for discrete variable in the non-stationary point processes. With the use of Dm it was shown that the maintained activity of the neurons of the mesencephalic reticular formation and red nucleus (tonic neuron groups) revealed higher order and larger values of Markov properties than that of the optic tract (OT) fibers and lateral geniculate nucleus neurons (phasic neuron groups) in cats. By employing Dm(t) it was shown that the value of the 1st order Markov properties of OT spike trains induced by the light spot presentation became to increase earlier in Y-fibers than in X-fibers; and that the value for Y-fibers returned to the maintained level in a short time, while the maximum value for X-fibers continued up to the light-off. The differentiation is considered to have a decided functional significance. From these results it is suggested that dependency code represents the stability of neuronal functions.

Purification and characterization of butyrylcholine-hydrolyzing enzyme from Pseudomonas polycolor

A butyrylcholine-hydrolyzing enzyme (EC 3.1.1.-) fo Pseudomonas polycolor IFO 3918 was purified approximately 9270-fold with a recovery of 9.9% by use of chromatographic techniques. The enzyme preparation appeared to be homogeneous when subjected to electrophoretic and ultracentrifugational analyses. The molecular weight was determined as approximately 59000 by gel filtration. Isoelectric focusing electrophoresis revealed that the enzyme had an isoelectric point around pH 5.1. The enzyme catalyzed the hydrolysis of butyrylcholine with the miximum activity among various esters tested, and split benzoylcholine, propionylcholine and some aliphatic esters, but did not attact acetylcholine. The estimated value of Km at pH 7.5 and 25 degrees C was 7-10(-4) M for butyrylcholine. The enzyme was irreversibly inhibited by organophosphorus compounds and carbamates, such as diisopropylphosphofluoridate and eserine. The enzyme was inhibited by some compounds, such as atropine and quinidine. Auaternary ammonium salts showed an inhibitory effect on the enzyme resembling co-operative inhibition.

Alcohol oxidases of Kloeckera sp. and Hansenula polymorpha. Catalytic properties and subunit structures

1. Alcohol oxidase (alcohol: oxygen oxidoreductase) of a thermophilic methanol-utilizing yeast, Hansenula polymorpha DL-1, was isolated in crystalline form. 2. This alcohol oxidase of H. polymorpha was more stable to heat than was the enzyme of Kloeckera sp. This difference in heat stability is compatible with the difference in growth temperatures for both yeasts. 3. The crystalline alcohol oxidases of both yeast oxidized the lower primary alcohols (C-2 to C-4) as well as methanol. The apparent Km values for the methanol of Kloeckera and H. polymorpha enzymes were 0.44 and 0.23 mM, respectively. The enzymes could also oxidize formaldehyde to formate, and were inactivated by relatively low concentrations of hydrogen peroxide. 4. The molecular weight for both enzymes was calculated to be about 670000. Each enzyme is composed of eight identical subunits (molecular weight 83000) and contains eight moles of FAD as the prosthetic group. The NH2-terminal and COOH-terminal amino acids of H. polymorpha enzyme were identified as alanine and phenylalanine, respectively. The octameric subunits model of each enzyme was confirmed by electron micrographs, which showed an octad aggregate, composed of two tetragons face to face.

A butyrylcholinesterase inhibitor produced by Penicillium sp. no. C-81 and its identity with mycelianamide

A screening aimed at obtaining a cholinesterase inhibitor of microbial origin was carried out using Pseudomonas butyrylcholinesterase. A mycelium-extract of a fungus strain, belonging to the genus Penicillium, was found to produce such an enzyme inhibitor. The inhibitor was purified and crystallized as colorless leaflets. From physical and chemical studies, the inhibitor was identified as being identical with an antibiotic, mycelianamide, though this compound was not known to have enzyme inhibitor activity. The kinetics of the inhibition of Pseudomonas butyrylcholinesterase were also studied. Horse serum cholinesterase and hog liver carboxylesterase were also inhibited by the isolated Penicillium C-81 inhibitor, but lipase and acetylcholinesterase were not.