Glycoproteins containing hexosamine in bean leaves

Abstract

During normal bean leaf growth, there was almost no change in the solubility classes of glycoprotein. Chloroplasts from mature leaves contained one-third of the insoluble glycoprotein. Glucosamine feeding produced a 10-fold increase in the insoluble glycoprotein of chloroplasts within 16 h. This was accompanied by the appearance of particles surrounding the starch grains and a considerable decrease in starch content.The low and fairly uniform levels of glycoproteins in growing leaves suggest that they play consistent structural or enzymic role rather than serving as reserve foodstuffs as in seeds. However, the abrupt increase in chloroplast glycoprotein upon feeding glucosamine indicates that the synthesis of this special glycoprotein is limited by endogenous precursors.