6M6T

Amylomaltase from Streptococcus agalactiae in complex with acarbose

Summary for 6M6T

• Entry DOI: 10.2210/pdb6m6t/pdb
• Related PRD ID: PRD_900007 PRD_900110
• Descriptor: 4-alpha-glucanotransferase, 4,6-dideoxy-4-{[(1S,4R,5S,6S)-4,5,6-trihydroxy-3-(hydroxymethyl)cyclohex-2-en-1-yl]amino}-alpha-D-glucopyranose-(1-4)-1,5-anhydro-D-glucitol, 4,6-dideoxy-4-{[(1S,4R,5S,6S)-4,5,6-trihydroxy-3-(hydroxymethyl)cyclohex-2-en-1-yl]amino}-alpha-D-glucopyranose-(1-4)-alpha-D-glucopyranose, ... (5 entities in total)
• Functional Keywords: amylomaltase, 4-alpha-glucanotransferase, cyclodextrin, acarbose, transferase
• Biological source: Streptococcus agalactiae
• Total number of polymer chains: 8
• Total formula weight: 479981.52

Authors

Wangkanont, K.,Tumhom, S.,Pongsawasdi, P. (deposition date: 2020-03-16, release date: 2021-03-31, Last modification date: 2023-11-29)

Primary citation

Tumhom, S.,Nimpiboon, P.,Wangkanont, K.,Pongsawasdi, P.
Streptococcus agalactiae amylomaltase offers insight into the transglycosylation mechanism and the molecular basis of thermostability among amylomaltases.
Sci Rep, 11:6740-6740, 2021

PubMed Abstract: Amylomaltase (AM) catalyzes transglycosylation of starch to form linear or cyclic oligosaccharides with potential applications in biotechnology and industry. In the present work, a novel AM from the mesophilic bacterium Streptococcus agalactiae (SaAM), with 18-49% sequence identity to previously reported AMs, was characterized. Cyclization and disproportionation activities were observed with the optimum temperature of 30 °C and 40 °C, respectively. Structural determination of SaAM, the first crystal structure of small AMs from the mesophiles, revealed a glycosyl-enzyme intermediate derived from acarbose and a second acarbose molecule attacking the intermediate. This pre-transglycosylation conformation has never been before observed in AMs. Structural analysis suggests that thermostability in AMs might be mainly caused by an increase in salt bridges since SaAM has a lower number of salt bridges compared with AMs from the thermophiles. Increase in thermostability by mutation was performed. C446 was substituted with A/S/P. C446A showed higher activities and higher k/K values for starch in comparison to the WT enzyme. C446S exhibited a 5 °C increase in optimum temperature and the threefold increase in half-life time at 45 °C, most likely resulting from H-bonding interactions. For all enzymes, the main large-ring cyclodextrin (LR-CD) products were CD24-CD26 with CD22 as the smallest. C446S produced more CD35-CD42, especially at a longer incubation time.

PubMed: 33762620
DOI: 10.1038/s41598-021-85769-3

Experimental method

X-RAY DIFFRACTION (2.75 Å)