Release of molybdenum co-factor from nitrate reductase and xanthine oxidase by heat treatment

Abstract

Heat treatment (90 sec at 70°) is shown to convert the bound molybdenum co-factor of tobacco cell-free extracts and bovine milk xanthine oxidase into a form capable of complementing the Neurospora crassa mutant nit-1.In the presence of 1 mM ascorbic acid, 25 mM molybdate and, for plant extracts, sulphydryl group protecting agents, the molybdenum co-factor can survive incubations up to 100° whilst maintaining its biological activity. Especially with plant extracts, the efficiency of heat treatment is considerably higher than that of the acidification procedure which is often utilized for releasing molybdenum co-factor.