Intermediary Metabolism of the Amino Acids

Meister, Alton

doi:10.1016/b978-0-12-395523-4.50008-3

Cited by 171 publications

(187 citation statements)

References 2,215 publications

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“…The keto acid may then racemize nonenzymatically by enolization to the dl-keto acid; on transamination a mixture of L-isoleucine and L-alloisoleucine would be obtained (23,24). Since D-alloisoleucine shares a common keto acid intermediate with L-isoleucine, the conversion from D-alloisoleucine to L-alloisoleucine could be explained in the same way.…”

Section: Discussionmentioning

confidence: 99%

Branched-Chain Amino Acid Substitutions in the Biosynthesis of the Antibiotic Actinomycin

Yajima

Mason

Katz

1975

Antimicrob Agents Chemother

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Actinomycins normally contain N-methyl-L-valine and either D-valine, Dalloisoleucine or both amino acids in the molecule. During antibiotic formation in a medium supplemented with one of the four isoleucine stereoisomers, Streptomyces parvulus and S. chrysomallus form complex actinomycin mixtures (Cl, C2, C3, El, and E2-like compounds). Although chromatographic techniques suggested that single homogeneous components had been isolated, subsequent studies indicated that such chromatographic fractions probably consisted of multiple isomers of actinomycin. Amino acid analyses revealed the presence of N-methylvaline and/or N-methylalloisoleucine and, in addition, D-isoleucine, D-valine, and D-alloisoleucine were frequently found in a given fraction.Schmidt-Kastner (30, 31) first noted that new actinomycins (El and E2) were synthesized by Streptomyces chrysomallus when the organism was grown in the presence of DL-isoleucine. It was reported (30, 31) that one or two residues of N-methylisoleucine replaced one or two residues of N-methylvaline, respectively, in the parent compound, actinomycin C3. More recently, our laboratory demonstrated that S. antibioticus and S. chrysomallus both form actinomycin mixtures which contain appreciable amounts of D-isoleucine and N-methyl-Lalloisoleucine (rather than N-methyl-isoleucine) when synthesis occurs with an isoleucine stereoisomer (15,35). N-methyl-L-alloisoleucine and D-isoleucine substitute for N-methyl-Lvaline and either D-valine or D-alloisoleucine, respectively, in the antibiotic peptides. Individual biosynthetic actinomycins were not examined; therefore, we initiated studies to establish the branched-chain amino acid composition of the isoleucine-induced actinomycin components formed by S. chrysomallus and S. parvulus. MATERIALS AND METHODSOrganisms and conditions of cultivation. S. chrysomallus (ATCC 11523) and S. parvulus (ATCC 12434) were maintained on slants of glucose-yeast extract-malt extract agar medium (9). Incubation was for 3 to 5 days at 30 C until sporulation had occurred; slants were then kept at 4 C until further use.For production of actinomycin the organisms were

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Section: Discussionmentioning

confidence: 99%

Branched-Chain Amino Acid Substitutions in the Biosynthesis of the Antibiotic Actinomycin

Yajima

Mason

Katz

1975

Antimicrob Agents Chemother

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“…It has been known for many years that choline is oxidized by liver mitochondria to betaine and that betaine serves as a methyl donor to homocysteine in the formation of methionine (Meister, 1965;Skiba et al, 1982). Since choline deficiency exerts a carcinogenic action only in liver, (Rogers & Newberne, 1980) it is noteworthy that the enzyme, betaine-homocysteine methyltransferase, is active only in liver (Stekol, 1955;Meister, 1965).…”

Section: Effects Of Choline Deficiencymentioning

confidence: 99%

“…Since choline deficiency exerts a carcinogenic action only in liver, (Rogers & Newberne, 1980) it is noteworthy that the enzyme, betaine-homocysteine methyltransferase, is active only in liver (Stekol, 1955;Meister, 1965). These conditions prompt the suggestion that the integrity of liver metabolism is dependent on methionine, and that choline is effective for this purpose in so far as it provides the methyl group for methionine synthesis in this organ.…”

Section: Effects Of Choline Deficiencymentioning

confidence: 99%

5-Methylcytosine depletion during tumour development: An extension of the miscoding concept

Nyce¹,

Weinhouse²,

Magee³

1983

Br J Cancer

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Perhaps the most ubiquitous aspect of tumours and the neoplastic cells of which they are composed is their loss of the ability to control cellular functions in a normal way. During the development of the malignant state, the neoplastic cell becomes increasingly refractory to both the internal and external stimulae which integrate its normal counterparts into functional tissues and organ systems. This lack of integration is associated with alterations in the expression of a host of gene products, including, for example, the ectopic biosynthesis of hormones (

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“…At the present time, little is known about the factors in cell oxidative deaminase (12). During this reaction, hydrogen peroxide is generated.…”

Section: Discussionmentioning

confidence: 99%

Oxygen sensitivity of an Escherichia coli mutant

1992

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Genetic evidence indicates that Oxys-6, an oxygen-sensitive mutant of Escherichia coli AB1157, is defective in the region of the hemB locus. Oxys-6 is capable of growth under aerobic conditions only if cultures are initiated at low-inoculum levels. Aerobic liquid cultures are limited to a cell density of 10(7) cells per ml by the accumulation of a metabolically produced, low-molecular-weight, heat-stable material in complex organic media. Both Oxys-6 and AB1157 cells produce the material, but only aerobic cultures of the mutant are inhibited by it. The material is produced by both intact cells and cell extracts in complex media. This reaction also occurs when the amino acid L-lysine is substituted for complex media.

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Intermediary Metabolism of the Amino Acids

Cited by 171 publications

References 2,215 publications

Branched-Chain Amino Acid Substitutions in the Biosynthesis of the Antibiotic Actinomycin

Branched-Chain Amino Acid Substitutions in the Biosynthesis of the Antibiotic Actinomycin

5-Methylcytosine depletion during tumour development: An extension of the miscoding concept

Oxygen sensitivity of an Escherichia coli mutant

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