PURIFICATION AND CHARACTERIZATION OF POLY(GAMMA-GLUTAMIC ACID) HYDROLASE FROM A FILAMENTOUS FUNGUS, MYROTHECIUM SP TM-4222

Poly(gamma-glutamic acid) (PGA) hydrolase was purified from the culture filtrate of a filamentous fungus, Myrothecium sp. TM-4222 and its general properties, especially the mode of hydrolytic action on the gamma-glutamyl bond of PGA, were investigated. The purified preparation demonstrated a homogeneous band on an acidic slab gel of pH 4.3 with polyacrylamide gel electrophoresis. The enzyme showed its maximum activity at 37-degrees-C and at pH 5.0, being stable up to 40-degrees-C. The molecular mass was estimated to be 68 kDa by gel filtration. The hydrolytic action of the enzyme was specific for PGA, but not for other gamma-glutamyl peptides or amides. The enzyme converted 38% of the original PGA with an average molecular mass of 500 kDa to smaller peptides, and then depolymerized these fragments to a mixture of gamma-oligopeptides which consisted of only L-glutamic acid. L-Glutamic acid monomer was negligible in the reaction mixture. The remaining 62% of PGA was resistant to the enzyme action, in which D-glutamic acid was mainly detected. This study demonstrated a novel endo-type specificity of hydrolysis on PGA by the enzyme.