CHARACTERIZATION OF [¹⁴C]-STARCH DEGRADATION BY RHIZOPUS GLUCOAMYLASE

Abstract

The hydrolysis of [14C]‐labelled tobacco starch by Rhizopus niveus glucoamylase was investigated using thin‐layer and gel filtration chromatography. Hydrolysis was characterized by a period of rapid [14C]‐glucose release, representing 15–30% of the total radioactivity, followed by a prolonged period of slow [14C]‐glucose release. Pullulanase enhanced [14C]‐glucose release, suggesting the presence of α‐(1→6) branch points. Thin‐layer chromatography was used as a rapid screening method for detecting glucoamylase activity in fractions eluted from a DEAE column of a Thermomyces lanuginosus culture filtrate, and gave results comparable to a coupled enzymatic method. [14C]‐Labelled starch from Canna leaf was less susceptible to amylolytic digestion than [14C]‐labelled tobacco starch.