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°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).