Vibrio vulnificus glycogen branching enzyme preferentially transfers very short chains: N1 domain determines the chain length transferred.

The glycogen branching enzyme from Vibrio vulnificus (VvGBE) transfers short side chains (DP 3-5) significantly greater than any other bacterial glycogen branching enzyme (GBE). To elucidate the role of the N-domain of VvGBE in the unique branching pattern, domain-truncated (N1 and N) and N1-domain-swapped (with VvGBE N1 replacing the counter part of Escherichia coli GBE) mutants were constructed. The truncation mutants synthesized branched products with a greatly reduced proportion of short chains. The swapping mutant exhibited a branching pattern of the short chain region similar to that of VvGBE. We conclude that the N1-domain of VvGBE has a crucial role in the determination of the branching pattern of glycogen.