CONIDIAL ALKALINE-PHOSPHATASE FROM NEUROSPORA-CRASSA

An alkaline phosphatase was purified from conidia of a Neurospora cras sa wild type strain. The M(r) of the purified native enzyme was estima ted as ca 145 000 and 110 000 by gel filtration, in the presence and a bsence of magnesium ions, respectively. A single polypeptide band of M (r) 36 000 was detected by SDS-PAGE, suggesting that the native enzyme was a tetramer of apparently identical subunits. Conidial alkaline ph osphatase was an acidic protein (pl = 4.0 +/- 0.1), with 40% carbohydr ate content. Optimal pH was affected by substrate concentration and ma gnesium ions. Low concentrations of calcium ions (0.1 mM) had slight s timulatory effects, but in excess (5 mM) caused protein aggregates wit h decreased activity. The enzyme specificity against different substra tes was compared with those reported for constitutive or Pi-repressibl e alkaline phosphatases produced by N. crassa. The results suggested t hat the conidial alkaline phosphatase represented a different class am ong other such enzymes synthesized by this organism.