[Effects of the isoenzymes of endoglucanase from Trichoderma longibrachiatum differing in their ability to be adsorbed on cellulose and on soluble, amorphous and crystalline substrates: a different role of adsorption efficiency].

The mode of action of two purified endoglucanase (Mr 42 000) from Trichoderma longibrachiatum on soluble CM-cellulose as well as on amorphous and crystalline celluloses was studied. Both enzymes had the same Km values for CM cellulose (1.4 g/l), similar V values (51 and 47 mumole . min . mg of protein) and synthesized glucose and cellobiose from CM-cellulose in comparable amounts. However, the enzymes differed essentially in their ability to be adsorbed on soluble cellulose, i. e. their partition coefficients (cellulose surface/bulk solution) differed by one order of magnitude. When the enzyme concentrations on the cellulose surface were equal (in two independent experiments), the rate of degradation of amorphous (but not crystalline) cellulose was also almost identical. However, when crystalline cellulose was subjected to hydrolysis, the more tightly adsorbed enzyme revealed the initial solubilizing activity which was 20 times greater than that of the less tightly adsorbed enzyme (at the same endoglucanase activity on the surface). In the presence of high cellobiase concentrations sufficient to convert all intermediate cellobiose into glucose the effectively adsorbed endoglucanase was capable to convert at least 50% of crystalline cellulose to glucose.