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M Desrochers

Publications and source records attributed to M Desrochers.

26 records · Page 2Linked to original sources
PubMed1981

High Production of beta-Glucosidase in Schizophyllum commune: Isolation of the Enzyme and Effect of the Culture Filtrate on Cellulose Hydrolysis.

Optimization experiments with response surface statistical analysis were performed with Schizophyllum commune to obtain high beta-glucosidase yields. The factors in the optimization experiment were the concentrations of cellulose, peptone, and KH(2)PO(4). Their optimal values were 3.2, 3.0, and 0.2 g/100 ml, respectively. Enzyme assays revealed very high beta-glucosidase (22.2 U/ml) and cellobiase (68.9 U/ml) yields. The avicelase yield was low as compared with that from Trichoderma reesei. Mixtures of S. commune and T. reesei culture filtrates caused faster and more extensive saccharification of Avicel than could be achieved by either filtrate alone. A beta-glucosidase was isolated and purified from the optimized culture filtrate of S. commune. The electrophoretic mobility of the purified beta-glucosidase indicated a molecular weight of 97,000. The amino acid composition was similar to that of beta-glucosidase from T. reesei. The acidic (aspartate and glutamate) residues or their amides or both made up approximately 20% of the protein. The NH(2)-terminal amino acid of the enzyme was histidine.

Journal Article↗
PubMed1978

Mapping of the hemE locus in Salmonella typhimurium.

A new type of heme-deficient mutant was isolated in Salmonella typhimurium by neomycin selection. The mutant was deficient in uroporphyrinogen decarboxylase activity, coded by the hemE gene. The hemE gene was located between the genes rif and thi at 128 min on the chromosomal map of S. typhimurium.

Carboxy-Lyases↗
PubMed1976

Porphobilinogen-accumulating mutants of Salmonella typhimurium LT2.

Four independent porphobilinogen-accumulating mutants of Salmonella typhimurium LT2 were isolated by selecting for dwarf colony formation on neomycin agar media. Cell-free extracts of the parent strain, but not of the mutants, were able to convert 5-aminolaevulinic acid or porphobilinogen to porphyrins. The results indicated that the mutants were deficient in uroporphyrinogen I synthase (EC. 4.3.I. 8) activity: these are the first mutants of this type reported in S. typhimurium LT2. Mapping of the hemC locus (for uroporphyrinogen I synthase) by F-mediated conjugation and by P22-mediated transduction showed the gene sequence ilvEDAC-hemC-cya-metE.

Aminolevulinic Acid↗
PubMed1976

Uroporphyrinogen III cosynthase-deficient mutant of Salmonella typhimurium LT2.

A new type of heme-deficient mutant of Salmonella typhimurium LT2 was isolated using neomycin. The mutant, designated as strain SASY74, accumulated uroporphyrin I and coproporphyrin I. Extracts of the mutant converted 5-aminolevulinic acid to uroporphyrin I. Extracts of the mutant SASY74 and of the uroporphyrinogen synthase-deficient mutant SASY32 complemented each other and converted, when incubated together, 5-aminolevulinic acid to protoporphyrin. This finding excludes the possibility that uroporphyrinogen I synthase in strain SASY74 is deficient in its cosynthase-binding ability. Hence, the most probable explanation for the accumulation of uroporphyrin I and coproporphyrin I by the mutant is the lack of the uroporphyrinogen III cosynthase activity. This mutant is the first isolated in bacteria with such deficiency, and the mutation is analogous, as far as porphyrin synthesis is concerned, to human congenital porphyria. Mapping of the corresponding gene (hemD) by conjugation and P22-mediated transduction suggests the following gene order on the chromosome: ilv....hemC, hemD, cya....metE. The hemC and hemD genes are probably adjacent; this is the first case in which two hem genes of Enterobacteriaceae are contiguous on the chromosomal map.

Catalase↗
PubMed1975

Hepatitis B antigen in Montréal blood donors: childhood institutionalization as an epidemiologic factor.

In 1971 the Canadian Red Cross blood tranfusion service instituted routine screening for HBAg of all blood donors, using nationwide a standardized counterimmunoelectrophoretic technique. The prevalence of carriers in the Province of Québec is unusually high (0.51%), being 3 to 12 times higher than in the other nine provinces. Among the carriers found in the Montréal area 289 volunteered to be seen by our group for an extensive interview and a series of laboratory tests. There were 243 men and 46 women; their ages ranged from 18 to 55, 90% being less than 40. Twenty-nine were of foreign origin and 260 were born in Canada. The epidemiologic data revealed that the reservoir of HBAg carriers among the blood donors of the Montréal area was found predominantly in the autochthonous population of French origin. Moreover, it appeared that 149 (52%) had lived in institution when they were infants or children: 127 were orphans and had been placed in institutions as newborns or babies, and 22 others had lived in institutions for at least 1 year between the ages of 5 and 10. This was by far the most important single epidemiologic factor that could contribute to the explanation of the abnormally high prevalence of HBAg carriers in the population studied.

Adolescent↗
PubMed1975

Uroporphyrin-accumulating mutant of Escherichia coli K-12.

An uroporphyrin III-accumulating mutant of Escherichia coli K-12 was isolated by neomycin. The mutant, designated SASQ85, was catalase deficient and formed dwarf colonies on usual media. Comparative extraction by cyclohexanone and ethyl acetate showed the superiority of the former for the extraction of the uroporphyrin accumulated by the mutant. Cell-free extracts of SASQ85 were able to convert 5-aminolevulinic acid and porphobilinogen to uroporphyrinogen, but not to copro- or protoporphyrinogen. Under the same conditions cell-free extracts of the parent strain converted 5-aminolevulinic to uroporphyringen, coproporphyrinogen, and protoporphyrinogen. The conversion of porphobilinogen to uroporphyrinogen by cell-free extracts of the mutant was inhibited 98 and 95%, respectively, by p-chloromercuribenzoate and p-chloromercuriphenyl-sulfonate, indicating the presence of uroporphyrinogen synthetase activity in the extracts. Spontaneous transformation of porphobilinogen to uroporphyrin was not detectable under the experimental conditions used [4 h at 37 C in tris(hydroxymethyl)aminomethane-potassium phosphate buffer, pH 8.2]. The results indicate a deficient uroporphyrinogen decarboxylase activity of SASQ85 which is thus the first uroporphyrinogen decarboxylase-deficient mutant isolated in E. coli K-12. Mapping of the corresponding locus by P1-mediated transduction revealed the frequent joint transduction of hemE and thiA markers (frequency of co-transduction, 41 to 44%). The results of the genetic analysis suggest the gene order rif, hemE, thiA, metA; however, they do not totally exclude the gene order rif, thiA, hemE, metA.

Acetates↗