Light‐mediated changes in the plastidic phosphorylase patterns in shoots of Pisum sativum

α‐1,4‐Glucan phosphorylase (EC 2.4.1.1) forms from light or dark grown shoots of Pisum sativum L. cv. ‘Kleine Rheinländerin’ have been studied using various electrophoretic techniques. The phosphorylase patterns of green and etiolated shoots differed. Etiolated shoots contained two enzyme forms, one residing inside and the other outside the etioplast; this was shown by electrophoresis of extracts of isolated etioplasts. Purity and intactness of the organelle preparation were ascertained by electron microscopy. Light‐grown shoots contained, in addition to these two enzyme forms, a third phosphorylase which appears to be chloroplast‐specific. The two plastidic phosphorylase forms differed slightly in their apparent molecular masses (as determined by non‐denaturing polyacrylamide gel electrophoresis) and in their affinities towards branched polyglucans (as revealed by affinity electrophoresis). The apparent affinity of the extrachloroplastic phosphorylase form to these polyglucans was orders of magnitude higher than that of the two plastidic enzyme forms. The development of the chloroplast‐specific phosphorylase pattern is under photocontrol. Investigations performed with red or far‐red illuminated wild‐type plants and with a pale mutant which has a highly reduced pigment and thylakoid content suggest that this photocontrol is mediated by phytochrome.