Influence of inorganic nitrate on the formation of extracellular protease and ribonuclease by Penicillium janthinellum

Abstract

The influence of nitrogen source on the formation of the extracellular acid protease and acid ribonuclease in shake cultures of the mold Penicillium janthinellum has been studied. It is observed that there is a long delay in the formation of the enzymes when nitrate is the sole source of nitrogen, but they are formed much earlier on other nitrogen sources such as ammonium salts, urea, or bacto-peptone. They are also formed earlier when nitrate is partially replaced by an ammonium salt. Small amounts of nitrite and hydroxylamine inhibit the formation of the enzymes when the mold is grown on ammonium lactate. When the mold is grown on nitrate, the culture filtrates contain inhibitory amounts of nitrite and hydroxylamine. The results indicate that the delayed formation of the enzymes in nitrate medium may be due to the formation of nitrite and hydroxylamine, which are inhibitory. The activities of the two enzymes are not inhibited by nitrite or hydroxylamine, in vitro. Prolonged preincubation of the enzymes with nitrite or hydroxylamine also does not affect the enzyme activities, indicating that it is the formation of the enzymes that is affected.