The function of the carbohydrate units of three fungal enzymes in their resistance to dehydration

Abstract

Glucose oxidase (from Aspergillus niger), glucoamylase (from Rhizopus spp.), and cellulase (from Aspergillus niger) of fungal origin are all glycosylated proteins. Dehydration of the three enzymes to a range of water potentials did not affect their activity. However, when more than 10% of the carbohydrate associated with the molecules was removed by periodate oxidation, the enzymes were highly susceptible to dehydration when compared with oxidized controls. Polyvinyl pyrrolidone and Dextran T500 protected the three enzymes in their oxidized state against the effects of dehydration.The carbohydrate units of the enzymes have a function in protecting the enzymes from dehydration and this may be a contributing factor to the survival of microorganisms in environments of low water potentials. The involvement of water associated with the enzyme molecules due to the presence of carbohydrate units is considered to be the protecting mechanism.