How many kinds od monomers are in starch?
. The synthesis of amylopectin (starch) 3.1 The role of starch-branching enzymes The existence of multiple isoforms of starch-branching enzymes offers a possible explanation for the polymodal distribution of branch lengths of amylopectin. This type of distribution might result from the simultaneous activities of two or more isoforms with different preferences for the length of chain transferred. Support for this idea comes from examination of the isoforms of starch-branching enzyme for which primary amino acid sequences are available. These can be divided on the basis of clear differences in sequence into two classes, referred to as A and B (Burton et al., 1995). Storage organs of, for example, pea, wheat, maize, rice and potato, possess members of both classes. Detailed studies of the A and B isoforms of maize endosperm in vitro and when expressed in Escherichia coli show that they do indeed differ in their preferences for the length of chain transferred (Guan and Preiss, 1993; Guan e
