Specific Inactivation of Fructose 1,6‐Bisphosphatase from Saccharomyces cerevisiae by a Yeast Protease

A fraction has been isolated from baker's yeast that is able to inactivate fructose 1,6‐bisphos‐phatase in vitro . The inactivating fraction is heat labile, non‐dialysable and is precipitated with ammonium sulfate; thus indicating that it is a protein. Malate dehydrogenase, hexokinase, glucose phosphate isomerase, glucose‐6‐phosphate dehydrogenase, glutamate dehydrogenase and catalase from baker's yeast and fructose 1,6‐bisphosphatase from the yeast Rhodotorula glutinis were not inactivated by the preparation. A fraction which is able to inhibit the inactivating factor has also been found in baker's yeast. The inhibitor is thermoresistant, non‐dialysable and precipitable by ammonium sulfate. The possible biological significance of these findings in relation with the regulation of yeast fructose 1,6‐bisphosphatase is considered.