One-carbon metabolism in Neurospora crassa wild-type and in mutants partially deficient in serine hydroxymethyltransferase.
1. The concentrations of folate-dependent enzymes in Neurospora crassa Lindegren A wild type (FGSC no. 853), Ser-l mutant, strain H605a (FGSC no. 118), and for mutant, strain C-24 (FGSC no. 9), were compared during exponential growth on defined minimal media. Both mutants were partially lacking in serine hydroxymethyltransferase, but contained higher concentrations of 10-formyltetrahydrofolate synthetase than did the wild type. Mycelia of the mutants contained higher concentrations of these enzymes when growth media were supplemented with 1mM-glycine. In the wild-type, this glycine supplement also increased the specific activities of 5,10-methylenetetrahydrofolate dehydrogenase and 5,10-methylenetetrahydrofolate reductase. 5. During growth, total folate and polyglutamyl folate concentrations were greatest in the wild-type. Methylfolates were not detected in mutant Ser-l, and were only present in the for mutant after growth in glycine-supplemented media. Exogenous glycine increased folate concentration threefold in the wild type, mainly owing to increases in unsubstituted polyglutamyl derivatives. 3. Feeding experiments using 14C-labelled substrates showed that C1 units were generated from formate, glycine and serine in the wild type. Greater incorporation of 14C occurred when mycelia were cultured in glycine-supplemented media. Formate and serine were precursors of C1 units in the mutants, but the ability to cleave glycine was slight or lacking.
D000429:Alcohol Oxidoreductases / Q000378:metabolism; D000596:Amino Acids / Q000378:metabolism; D002244:Carbon / Q000378:metabolism*; D005492:Folic Acid / Q000378:metabolism; D005574:Formate-Tetrahydrofolate Ligase / Q000378:metabolism; D005561:Formates / Q000378:metabolism; D005998:Glycine / Q000378:metabolism; D012696:Glycine Hydroxymethyltransferase / Q000378:metabolism*; D008754:Methylenetetrahydrofolate Dehydrogenase (NADP) / Q000378:metabolism; D009154:Mutation; D009491:Neurospora / Q000378:metabolism*; D009492:Neurospora crassa / Q000201:enzymology / Q000378:metabolism*; D012694:Serine / Q000378:metabolism; D013045:Species Specificity; D013997:Time Factors; D014166:Transferases / Q000378:metabolism*
D000596:Amino Acids; D005561:Formates; D012694:Serine; D002244:Carbon; D005492:Folic Acid; D000429:Alcohol Oxidoreductases; D008754:Methylenetetrahydrofolate Dehydrogenase (NADP); D014166:Transferases; D012696:Glycine Hydroxymethyltransferase; D005574:Formate-Tetrahydrofolate Ligase; D005998:Glycine