STUDIES ON BIOSYNTHETIC ENZYMES: I. MUTANT FORMS OF HISTIDINOL DEHYDROGENASE FROM NEUROSPORA CRASSA

Abstract

Data are presented on the kinetic properties of the enzyme histidinol dehydrogenase obtained from the wild type Neurospora crassa and from 15 mutants. Differences were observed in pH curves and in Michaelis constants, both for histidinol and NAD. Ten mutants had modified affinity for NAD and three for histidinol, and one was modified in both these parameters. Two temperature-sensitive mutants were found to have an enzyme with a different activation energy from the normal. The data are discussed in relation to theories about whether histidinol dehydrogenase is a multifunctional enzyme in this organism or is part of an operon system.