• Journal of Microbiology and Biotechnology
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• v.18 no.8
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• pp.1401-1407
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• 2008

The roles of conserved amino acid residues (Va1329-Ala330-Asn331-Glu332), constituting an extra sugar-binding space (ESBS) of Thermus maltogenic amylase (ThMA), were investigated by combinatorial saturation mutagenesis. Various ThMA mutants were firstly screened on the basis of starch hydrolyzing activity and their enzymatic properties were characterized in detail. Most of the ThMA variants showed remarkable decreases in their hydrolyzing activity, but their specificity against various substrates could be altered by mutagenesis. Unexpectedly, mutant H-16 (Gly-Leu-Val-Tyr) showed almost identical hydrolyzing and transglycosylation activities to wild type, whereas K-33 (Ser-Gly-Asp-Glu) showed an extremely low transglycosylation activity. Interestingly, K-33 produced glucose, maltose, and acarviosine from acarbose, whereas ThMA hydrolyzed acarbose to only glucose and acarviosine-glucose. These results propose that the substrate specificity, hydrolysis pattern, and transglycosylation activity of ThMA can be modulated by combinatorial mutations near the ESBS.

• Proceedings of the Korean Society of Life Science Conference
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• 2003.05a
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• pp.23-37
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• 2003

A novel inhibitor against maltose-producing a-amylase was prepared via stepwise degradation of a high molecular weight acarbose (HMWA) using Thermus maltogenic amylase (ThMA). The structure of the purified inhibitor was determined to be ${\alpha}$-D-glucopyranosyl-${\alpha}$-acarviosinyl-D-glucopyranose (GlcAcvGlc). Progress curves of p-nitrophenyl-${\alpha}$-D-maltoside (PNPG2) hydrolysis by various amylolytic enzymes, including maltogenase (MGase), ThMA, and cyclodextrinase(CDase) I-5, in the presence of acarbose or GlcAcvGlc indicated a slow-binding mode of inhibition. The inhibition potency of GlcAcvGlc for MGase, ThMA, and CDase I-5 was 3 orders of magnitude higher than that of acarbose.

• Journal of Microbiology and Biotechnology
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• v.13 no.6
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• pp.969-975
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• 2003

Two conserved amino acid residues in the extra sugar-binding space near the catalytic site of Thermus maltogenic amylase (ThMA) were analyzed for their role in the hydrolysis and transglycosylation activity of the enzyme. Site-directed mutagenesis was carried out by replacing N33l with a lysine (N331K), E332 with a histidine (E332H), or by replacing both residues at the same time (N331K/E332H). The measured $K_m$ values indicated that affinities toward all substrates tested, including starch, pullulan, ${\beta}-cyclomaltodextrin$, and acarbose, were lower in all the mutants compared to that of wild-type ThMA, leading to reduced hydrolysis activity. In addition, the lower ratio of transglycosylation to hydrolysis in the mutants compared to that in the wild-type ThMA indicated that these mutants preferred hydrolysis to the transglycosylation reaction. These results demonstrated that the conserved dipeptide at 331 and 332 of ThMA is directly involved in the formation and accumulation of transfer products by accommodating acceptor sugar molecules.

• Microbiology and Biotechnology Letters
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• v.44 no.3
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• pp.363-369
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• 2016

A putative cyclomaltodextrinase gene (licd) was found from the genome of Listeria innocua ATCC 33090. The licd gene is located in the gene cluster involved in maltose/maltodextrin utilization, which consists of various genes encoding maltose phosphorylase and sugar ABC transporters. The structural gene encodes 591 amino acids with a predicted molecular mass of 68.6 kDa, which shares less than 58% of amino acid sequence identity with other known CDase family enzymes. The licd gene was cloned, and the dimeric enzyme with C-terminal six-histidines was successfully produced and purified from recombinant Escherichia coli. The enzyme showed the highest activity at pH 7.0 and 37℃. licd could hydrolyze β-cyclodextrin, starch, and maltotriose to mainly maltose, and it cleaved pullulan to panose. It could also catalyze the hydrolysis of acarbose to glucose and acarviosine-glucose. In particular, it showed significantly higher activity towards β-cyclodextrin and maltotriose than towards starch and acarbose. licd also showed transglycosylation activity, producing α-(1,6)- and/or α-(1,3)-linked transfer products from the acarbose donor and α-methyl glucopyranoside acceptor.

• Korean Journal of Microbiology
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• v.53 no.3
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• pp.208-215
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• 2017

A cyclomaltodextrinase (SPCD) gene was cloned from Streptococcus pyogenes ATCC 700294. Its open reading frame consists of 567 amino acids (66.8 kDa), which shows less than 37% of amino acid sequence identity with the other CDase-family enzymes. The homo-dimeric SPCD with C-terminal six-histidines was expressed and purified from Escherichia coli. It showed the highest activity at pH 7.5 and $45^{\circ}C$, respectively. SPCD has the broad substrate specificities against ${\beta}$-cyclodextrin, starch, and maltotriose to produce mainly maltose, whereas it hydrolyzes pullulan to panose. It can also catalyze the hydrolysis of acarbose to glucose and acarviosine-glucose. Interestingly, it showed much higher activity on ${\beta}$-cyclodextrin and acarbose than that on starch, pullulan, or maltotriose, which makes SPCD distinguished from common CDase-family enzymes. Although SPCD has significantly high acarbose-hydrolyzing activity, it showed negligible transglycosylation activity.

• Food Science and Biotechnology
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• v.18 no.3
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• pp.776-781
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• 2009

A putative cyclomaltodextrinase (BHCD) gene was found from the genome of Bacillus halodurans C-125, which encodes 578 amino acids with a predicted molecular mass of 67,279 Da. It shares 42-59% of amino acid sequence identity with common cyclomaltodextrinase (CDase)-family enzymes. The corresponding gene was cloned by polymerase chain reaction (PCR) and the dimeric enzyme with C-terminal 6-histidines was successfully overproduced and purified from recombinant Escherichia coli. BHCD showed the highest activity against ${\beta}-CD$ at pH 7.0 and $50^{\circ}C$. Due to its versatile hydrolysis and transglycosylation activities, BHCD has been confirmed as a member of CDases. However, BHCD can be distinguished from other typical CDases on the basis of its novel multisubstrate specificity. While typical CDases have over 10 times higher activity on ${\beta}-CD$ than starch or pullulan, the CD-hydrolyzing activity of BHCD is only 2.3 times higher than pullulan. In particular, it showed significantly higher activity ratio of maltotriose to acarbose than other common CDase-family enzymes.