- Volume 5, Issue 4, 1951

SUMMARY: A study (Fincham, 1950 of two mutant strains of Neurospora crassa, which probably owed their origin to independent occurrences of mutation at the same locus, showed them to be deficient in their ability to synthesize from ammonia the α-amino groups of a wide range of amino-acids. They grew well when any one of a number of different α-amino-acids was added to the medium, but would only grow slowly, and after a prolonged lag-phase, in the absence of amino-acid. The corresponding d-amino-acids and α-keto-acids were inactive in promoting growth. The mutants were subnormal in their capacity to assimilate ammonium nitrogen. In the present study the l-glutamic acid dehydrogenase activity of dialysed extracts of strains carrying the amination-deficiency mutation, and of a number of other wild-type and mutant strains, was investigated. All strains, with the exception of the amination-deficient strains, yielded an l-glutamic acid dehydrogenase specific for coenzyme II. Extracts of four amination-deficient strains had no detectable glutamic dehydrogenase activity, and did not inhibit the enzyme appreciably when added to wild-type extracts. Glucose-6-phosphate dehydrogenase was present in one extract tested for its presence.