The Intracellular Location of Phosphorylase in Tobacco (Nicotiana Tabacum L.).

Abstract

In centrifuged leaf homo-genates of healthy tobacco plants, phosphorylase activity, measured as hydrolyzed from glucose-1-P, was found to be mostly in the plastid free supernatant but more concentrated in the residue. When dark starved leaves were used no activity was in the residue. In full sun leaves a positive correlation was found between chlorophyll or protein and phosphorylase activity. In dark starved leaves the correlation was negative. This is taken as evidence that phosphorylase may be either in the plastid or external to it. A hypothesis is made that starch forms only in the plastid because this is the sole site of the formation of the glucose-1-P substrate. When glucose-1-P is supplied to the cell, amylose may form outside of the plastid.