Complete hydrolysis of myo-inositol hexakisphosphate by a novel phytase from Debaryomyces castellii CBS 2923.

Debaryomyces castellii phytase was purified to homogeneity in a single step by hydrophobic interaction chromatography. Its molecular mass is 74 kDa with 28.8% glycosylation. Its activity was optimal at 60 degrees C and pH 4.0. The K (m) value for sodium phytate was 0.532 mM. The enzyme exhibited a low specificity and hydrolyzed many phosphate esters. The phytase fully hydrolyzed myo-inositol hexakisphosphate (or phytic acid, Ins P(6)) to inositol and inorganic phosphate. The sequence of Ins P(6) hydrolysis was determined by combining results from high-performance ionic chromatography and nuclear magnetic resonance. D. castellii phytase is a 3-phytase that sequentially releases phosphate groups through Ins (1,2,4,5,6) P(5), Ins (1,2,5,6) P(4), Ins (1,2,6) P(3), Ins (1,2) P(2), Ins (1 or 2) P(1), and inositol (notation 3/4/5/6/1 or 2).