Effect of Added Primer on Lima Bean Phosphorylase

Abstract

FORMATION of an amylose-type polysaccharide from glucose-1-phosphate by the action of phosphorylase does not take place unless a small amount of starch, glycogen or dextrin is added as the priming agent. The primer, which is sometimes called activator, is required presumably because the enzyme is unable to cause the condensation of glucose-1-phosphate, but acts only by transferring glucose units from glucose-1-phosphate to the non-reducing end of an already existing polysaccharide chain¹. There have been reported, however, two exceptions which were claimed to require no added primer in this reaction; one is purified phosphorylase of lima bean, as reported by Green and Stumpf², and the other is that of sweet potato, as reported by Inoue and Onodera³. In both cases, according to these authors, the addition of different types of primers in various amounts had little or no effect on the initial velocity of this reaction catalysed by respective enzymes. In the case of purified lima bean phosphorylase, the possibility that the enzyme preparation might be contaminated with polysaccharide was excluded, since this preparation could not serve as a source of a polyhexose catalyst for purified potato enzyme.