The Enzymatic Synthesis of N-Methylglutamic Acid
1966; Elsevier BV; Volume: 241; Issue: 4 Linguagem: Inglês
10.1016/s0021-9258(18)96855-9
ISSN1083-351X
AutoresWilliam V. Shaw, Larry B. Tsai, Earl R. Stadtman,
Tópico(s)Enzyme Structure and Function
ResumoAbstract A species of Pseudomonas which grows on methylamine as the sole source of carbon and nitrogen was isolated from soil enrichment cultures. The lack of pigmentation in the organism and its unusual substrate specificity suggest that it is a species of Pseudomonas distinct from those previously isolated from one carbon substrate enrichments. When grown on methylamine, the new Pseudomonas sp. elaborates an enzyme that catalyzes a reaction between methylamine and l-glutamate to form a hitherto unknown biological intermediate, N-methylglutamate, and ammonia. The enzyme is absent from cells grown on glycerol and ammonia in the absence of methylamine. A number of possible reaction mechanisms to explain N-methylglutamate synthesis have been studied with the conclusion that the reaction is reversible and most likely proceeds by a direct displacement mechanism. Evidence from studies with 15N-labeled substrates are not compatible with a transmethylation mechanism. The possible role of N-methylglutamate synthetase in the one carbon metabolism of this organism is suggested by the results of pulse-labeling experiments showing the appearance of isotope from 14C-methylamine in N-methylglutamate, sarcosine, serine, alanine, and aspartate in the order indicated.
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