PURIFICATION AND CHARACTERIZATION OF AN EXTRACELLULAR THIOL-CONTAINING SERINE PROTEINASE FROM THERMOMYCES-LANUGINOSUS

An extracellular protease produced by the filamentous fungus Thermomyc es lanuginosus has been purified and characterized. The results indica te that the enzyme, which we have called humicolin, is a thiol-contain ing serine protease with a molecular mass of 38000 kilodaltons. Secret ion of humicolin, which is glycosylated, is tightly regulated by prote in substrates. Kinetic characterization has revealed that humicolin ac tivity is highly dependent upon the deprotonation of a group with a pK (a) of 6.6 and that the enzyme has a specificity for phenylalanine in the P1 position of the substrate.