Formation of Hydroxamates during Proteolysis by an Enzyme System from Yeast

Abstract

DURING re-investigation of an enzyme system, from yeast previously reported to form ‘activated’ peptides¹ extensive proteolysis was noted and enzyme-catalysed hydroxylaminolysis of protein was suspected as the source of hydroxamate formation². Acyl-enzyme complexes were visualized as intermediates rather than some form of ‘activated’ peptide originally suggested by Cooper et al.¹. The main evidence for the latter hypothesis had been the appearance, after paper electrophoresis of the products of the reaction in the absence of hydroxylamine, of a band which gave a positive reaction to the hydroxylamine ferric chloride test. This test, however, may be misleading when conducted on paper³. The formation of hydroxamates from protein substrates by other proteolytic enzymes was also demonstrated² and is presumably analogous to the well-known transamidation reactions recorded by many authors^4–8. Such reactions have only been unequivocally demonstrated using simple substrates but have been invoked to explain the formation of plasteins^9,10 and energy-independent incorporation of amino-acids into mitochondrial protein¹¹.