Classification of pullulanase as an exoenzyme by means of gas chromatography

Abstract

Pullulanase from Aerobacter aerogenes is a glucosidase specifically splitting α‐1,6‐glycosidic bonds. A polymeric substrate for the pullulanase is the linear α‐glucan pullulan from Pullularia pullulans.This α‐glucan consists of maltotriose units linked together by α‐1,6‐glycosidic bonds. This means that the polysaccharide is degraded by pullulanase to yield exclusively maltotriose. There are two possibilities of enzyme action:a) either the hydrolysis starts from one end of the linear chain directly setting free maltotriose;b) or random splitting occurs to give larger units of varying molecular weight which will finally be degraded to maltotriose.The decision between these two alternatives could be made by gas liquid chromatography. The quantity of liberated maltotriose rises linearly with the reaction time, which proves that hydrolysis occurs from the end of the substrate chain. This method using gas liquid chromatography as an analytical tool may also be applied to monitor the action of other hydrolytic enzymes, as it could be shown for α‐ and β‐amylase.