The Aspergillus nidulans pyrG89 mutation alters glycosylation of secreted acid phosphatase

The glycosylation level of the pacA-encoded acid phosphatase secreted by Aspergillus nidulans was reduced in strains pabaA1 pyroA4and pabaA1 pyroA4 pyrG89, compared to strains carrying these mutations singly. The molecular mass of the enzyme secreted by the triple mutant grown at pH 5.0 was 105 and 45 kDa as determined by exclusion chromatography and SDS-PAGE, respectively. In contrast, the pabaA1 strain secreted acid phosphatases of 119 and 62 kDa. The enzyme also had an altered electrophoretic mobility and glycosylation had a protective effect against its heat inactivation. Thus, this combination of mutants alters glycosylation of the enzyme, leading to changes in their structural properties. In spite of this, no deviation was observed in the apparent optimum pH and Michaelis kinetics for enzymatic hydrolysis of p-nitrophenyl phosphate or alpha-naphthyl phosphate.