Characterization of a Novel Maltose-Forming α‑Amylase from Lactobacillus plantarum subsp. plantarum ST-III

• Published in: Journal of agricultural and food chemistry 2016-03, Vol.64 (11), p.2307-2314
• Main Authors: Jeon, Hye-Yeon, Kim, Na-Ri, Lee, Hye-Won, Choi, Hye-Jeong, Choung, Woo-Jae, Koo, Ye-Seul, Ko, Dam-Seul, Shim, Jae-Hoon
• Format: Article
• Language: English
• Subjects: alpha-Amylases - chemistry; alpha-Amylases - genetics; alpha-Amylases - metabolism; Cyclodextrins - metabolism; Escherichia coli - genetics; Hydrolysis; Kinetics; Lactobacillus plantarum - enzymology; Maltose - analogs & derivatives; Maltose - metabolism; Recombinant Proteins - metabolism; Substrate Specificity; Trisaccharides - metabolism
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/acs.jafc.5b05892

A novel maltose (G2)-forming α-amylase from Lactobacillus plantarum subsp. plantarum ST-III was expressed in Escherichia coli and characterized. Analysis of conserved amino acid sequence alignments showed that L. plantarum maltose-producing α-amylase (LpMA) belongs to glycoside hydrolase family 13. The recombinant enzyme (LpMA) was a novel G2-producing α-amylase. The properties of purified LpMA were investigated following enzyme purification. LpMA exhibited optimal activity at 30 °C and pH 3.0. It produced only G2 from the hydrolysis of various substrates, including maltotriose (G3), maltopentaose (G5), maltosyl β-cyclodextrin (G2-β-CD), amylose, amylopectin, and starch. However, LpMA was unable to hydrolyze cyclodextrins. Reaction pattern analysis using 4-nitrophenyl-α-d-maltopentaoside (pNPG5) demonstrated that LpMA hydrolyzed pNPG5 from the nonreducing end, indicating that LpMA is an exotype α-amylase. Kinetic analysis revealed that LpMA had the highest catalytic efficiency (k cat/K m ratio) toward G2-β-CD. Compared with β-amylase, a well-known G2-producing enzyme, LpMA produced G2 more efficiently from liquefied corn starch due to its ability to hydrolyze G3.