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W R Martin

Publications and source records attributed to W R Martin.

At least 253 records · Page 14Linked to original sources
PubMed1966

Metabolism of 6-Mercaptopurine by Resistant Escherichia coli Cells.

Coggin, Joseph H. (University of Chicago, Chicago, Ill.), Muriel Loosemore, and William R. Martin. Metabolism of 6-mercaptopurine by resistant Escherichia coli cells. J. Bacteriol. 92:446-454. 1966.-6-Mercaptopurine (MP) utilization as a source of purine in MP-sensitive and -resistant cultures of Escherichia coli was investigated. The label of MP-8-C(14) appeared in adenine and guanine of ribonucleic acid and deoxyribonucleic acid in sensitive and resistant cultures. Studies using MP-S(35) further demonstrated that the MP moiety was degraded, as shown by a rapid decrease in radioactivity from cells upon exposure to MP for 20 min. Enzymatic analysis showed that MP was converted to 6-mercaptopurine ribonucleotide (MPRP) by extracts derived from both sensitive and resistant cells. Resistant cell preparations, however, degraded MPRP to inosine monophosphate (IMP) rapidly when compared with analogue degradation by sensitive cells. Inosineguanosine-5'-phosphate pyrophosphorylase from resistant cells did not catalyze the synthesis of IMP from hypoxanthine when the cells were cultured in the presence of MP, but these enzyme preparations actively converted guanine to guanosine monophosphate (GMP). Pyrophosphorylase derived from resistant cells cultured in medium without MP catalyzed the conversion of hypoxanthine to IMP and also guanine to GMP. These observations suggest that inosine-guanosine-5'-phosphate pyrophosphorylase is composed of two distinct enzymes. The mode of resistance to MP in E. coli is related to an enhancement of the enzymatic degradation of MPRP to the pivotal purine intermediate, IMP.

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PubMed1961

PATHWAY FOR THE DISSIMILATION OF ITACONIC AND MESACONIC ACIDS.

Brightman, Vernon (The University of Chicago, Chicago), and William R. Martin. Pathway for the dissimilation of itaconic and mesaconic acids. J. Bacteriol. 82:376-382. 1961.-Studies on the oxidation of itaconic and mesaconic acids by a Pseudomonas sp., adapted to utilize either of these acids as a sole carbon source, have provided evidence for a pathway converting both itaconate and mesaconate to succinate. A metabolic interconversion of itaconate, mesaconate, and citramalate has also been demonstrated by whole cell and cell-free enzyme studies. Succinate derived from methylene-labeled itaconate was found to be labeled in the inside carbon atoms, a fact which indicates that the branched chain compound was converted into a straight chain molecule by a shift of the methylene carbon (C-5) from the side chain of itaconate to a position between C-2 and C-3 in an, as yet, unknown straight chain intermediate prior to its conversion to succinate.

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