Maize branching enzyme catalyzes synthesis of glycogen-like polysaccharide in glgB-deficient Escherichia coli.

Abstract

The structure of a-glucan, isolated from wild-type Escherichia coli B, a glycogen branching enzyme (BE)-deficient E. coli AC71 (glgB-), or from AC71 transformed with genes coding for maize BEI and BEII individually as well as with both genes, was analyzed by high-performance anion-exchange chromatography (HPAEC) with pulsed amperometric detection. Transformation of the maize BE gene(s) in AC71 (glgB-) showed complementation in branching activity. Analysis by HPAEC revealed different structures between glycogen ofE. coli B and a-glucan of AC71 transformed with a different maize BE gene(s). The individual chains of the ci-glucan debranched with isoamylase were distributed between chain length (CL) 3 and > 30 and the chain with CL 6 was the most abundant. In comparison with the glycogen ofE. coli B, the az-glucan of AC71 transformed with the maize BE gene(s) consisted ofa lesser amount of chains with CL 7-9 and a larger amount ofchains with CL > 14. It also showed a broad peak with chains of CL 9-12 as in maize amylopectin. This study provides in vivo evidence that glycogen BE and maize BE isozymes may have different specificities in the length of chain transferred. Furthermore, this study suggests that the specificity of glycogen synthase and starch synthase and their concerted action with BE play an important role in determining the structure of the polysaccharide synthesized.

A review of starch‐branching enzymes and their role in amylopectin biosynthesis

“…In cereals, the SBEII class is subdivided into two distinct gene products, SBEIIa and SBEIIb, each with different kinetic characteristics and tissue expression patterns. SBEII isoforms transfer shorter chains (DP [6][7][8][9][10][11][12][13][14] and prefer amylopectin as a substrate (29). These characteristics have also been shown in a variety of other plant species, for example, rice (Oryza sativa L.; ref.…”

“…The different catalytic and kinetic characteristics associated with plant SBEs have implications for their different roles in starch synthesis. Minimum chainlength requirement for branching differs between the SBEI and SBEII classes (13,28). The minimum glucan chain-length requirement for branching by maize (Zea mays L.) SBEI is a degree of polymerization (DP) of 15, whereas for the SBEII class, it is DP 12.…”

Importance of isoforms of starch‐branching enzyme in determining the structure of starch in pea leaves

“…The properties of the two classes are distinct. The class A isoform from maize endosperm (isoform II) has a lower affinity for amylose in vitro than the class B isoform (isoform I), and creates branches in vitro and in an Escherichia coli expression system which are on average shorter than those created by the class B isoform (Guan and Preiss, 1993;Guan et aL, 1995;Takeda et aL, 1993a). Although isoforms from other organs are less well studied, there are good indications that these properties are characteristic of A and B isoforms generally (Burton et aL, 1995;Smith, 1988).…”

Recent Progress toward Understanding Biosynthesis of the Amylopectin Crystal

“…Molecular cloning advances raise the possibility of reconstituting an amylopectin biosynthetic system with specific BE/SS combinations. In one relevant study, Escherichia coli was utilized to produce maize BEI and BEIIb in the same cells (Guan et al, 1995). The polymers produced in conjunction with the prokaryotic glucan synthase were distinct from amylopectin and resembled the relatively unordered molecule glycogen.…”