Thermostable conidial and mycelial alkaline phosphatases from the thermophilic fungus Scytalidium thermophilum

An extracellular (conidial) and an intracellular (mycelial) alkaline phosph atase from the thermophilic fungus Scytalidium thermophilum were purified b y DEAE-cellulose and Concanavalin A-Sepharose chromatography. These enzymes showed allosteric behavior either in the presence or absence of MgCl2, BaC l2, CuCl2, and ZnCl2. All of these ions increased the maximal velocity of b oth enzymes. The molecular masses of the conidial and mycelial enzymes, est imated by gel filtration, were 162 and 132 kDa, respectively. Both proteins migrated on SDS-PAGE as a single polypeptide of 63 and 58.5 kDa, respectiv ely, suggesting that these enzymes were dimers of identical subunits. The b est substrate for the conidial and mycelial phosphatases was p-nitrophenylp hosphate, but,beta -glycerophosphate and other phosphorylated compounds als o served as substrates. The optimum pH for the conidial and mycelial alkali ne phosphatases was 10.0 and 9.5 in the presence of AMPOL buffer, and their carbohydrate contents were about 54% and 63%, respectively. The optimum te mperature was 70-75 degreesC for both activities. The enzymes were fully st able up to 1 h at 60 degreesC. These and other properties suggested that th e alkaline phosphatases of S. thermophilum might be suitable for biotechnol ogical applications.