Open AccessEffects of Yeast Proteinase and Its Inhibitor on the Inactivation of Tryptophan Synthase from Saccharomyces cerevisiae and Neurospora crassa
Author(s) -
Tsai Hsin,
Tsai Jane H. J.,
Yu Peter H.
Publication year - 1973
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1973.tb03190.x
Subject(s) - neurospora crassa , biochemistry , saccharomyces cerevisiae , neurospora , yeast , biology , proteases , enzyme , tryptophan synthase , tryptophan , amino acid , gene , mutant
This paper reports the isolation of a proteinase and a proteinase inhibitor from Saccharomyces cerevisiae S288C (α). The purified proteinase catalyzes the hydrolysis of casein at neutral pH. It inactivates the holo‐tryptophan synthase from Neurospora crassa but does not inactivate the holo‐ornithine aminotransferase from pig kidney. This proteinase can be inhibited either by phenylmethanesulfonyl fluoride (a specific inhibitor for serine proteases), the sulfhydryl reagent, p ‐mercuribenzoate, or the endogenous proteinase inhibitor present in yeast. The yeast proteinase inhibitor is a heat‐stable material with a molecular weight of approximately 13000. This proteinase inhibitor can protect both yeast and Neurospora tryptophan synthase against proteolytic inactivation. The proteinase and its inhibitor coexist in the yeast extracts. The cellular level of the proteinase and the inhibitor activities varies with the composition of the medium in which the cells are grown. Since some yeast proteinases have been shown to form inactive complexes with their respective inhibitors, it is proposed that proteinase‐inhibitor interaction is a possible mechanism for regulation of intracellular proteolytic activity.