Extracellular Enzyme System Utilized by the Fungus Sporotrichum pulverulentum (Chrysosporium lignorum) for the Breakdown of Cellulose

Abstract

Five endo-1,4-beta-glucanases (EC 3.2.1.4) have been separated from culture solutions OF THE ROT FUNGUS Sporotrichum pulverulentum (formerly called Chrysosporium lignorum) grown on powder cellulose as the sole carbon source. They have been extensively purified and characterized with regard to some physicochemical properties. The purifications have been carried out on a quantitative basis, the purity of the enzymes being tested in several ways. After purification they all showed one single protein band in analytical polyacrylamide electrophoresis, on dodecyl-sulphate gels and in analytical isoelectric focusing on flat-bed polyacrylamide gels. One exo-1,4-beta-glucanase has also been identified in the culture solution and separated from the endo-1,4-beta-glucanases. From the data obtained during the quantitative purification it has been possible to calculate that the ratio of activity between the five endoglucanases T1, T2a, T2b, T3a, and T3b in the culture solutions is 4:1:1:1:1. It has also been calculated that the weight ratio endoglucanase protein to exoglucanase protein is approximately 1:1. Flat-bed isoelectric focusing has been used for the identification of the individual endoglucanases and a new zymogram technique, useful for studies of carbohydrases in general, has been developed. The molecular weights, determined by ultracentrifugation, and calculated on the basis of a knowledge of the amino acid composition and carbohydrate content vary between 28200 and 37500. Small but significant differences in the amino acid compositions of the different endoglucanases have been found. The carbohydrate content varies between 0 and 10.5%, all but one of the enzymes being glycoproteins. For two of these the exact carbohydrate composition has been determined. Enzyme T1 contains 2 glucose and 19 mannose units per enzyme molecule while enzyme T2b contains 5 mannose, 7 galactose, 1 glucose and 1 arabinose unit per molecule.