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Mar. Drugs 2018, 16(4), 120; https://doi.org/10.3390/md16040120

AlgM4: A New Salt-Activated Alginate Lyase of the PL7 Family with Endolytic Activity

1
Guangxi Key Laboratory of Marine Natural Products and Combinatorial Biosynethesis Chemistry, Guangxi Academy of Sciences, Nanning 530007, China
2
The Food and Biotechnology, Guangxi Vocational and Technical College, Nanning 530226, China
*
Author to whom correspondence should be addressed.
Received: 6 March 2018 / Revised: 3 April 2018 / Accepted: 3 April 2018 / Published: 6 April 2018
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Abstract

Alginate lyases are a group of enzymes that catalyze the depolymerization of alginates into oligosaccharides or monosaccharides. These enzymes have been widely used for a variety of purposes, such as producing bioactive oligosaccharides, controlling the rheological properties of polysaccharides, and performing structural analyses of polysaccharides. The algM4 gene of the marine bacterium Vibrio weizhoudaoensis M0101 encodes an alginate lyase that belongs to the polysaccharide lyase family 7 (PL7). In this study, the kinetic constants Vmax (maximum reaction rate) and Km (Michaelis constant) of AlgM4 activity were determined as 2.75 nmol/s and 2.72 mg/mL, respectively. The optimum temperature for AlgM4 activity was 30 °C, and at 70 °C, AlgM4 activity dropped to 11% of the maximum observed activity. The optimum pH for AlgM4 activity was 8.5, and AlgM4 was completely inactive at pH 11. The addition of 1 mol/L NaCl resulted in a more than sevenfold increase in the relative activity of AlgM4. The secondary structure of AlgM4 was altered in the presence of NaCl, which caused the α-helical content to decrease from 12.4 to 10.8% and the β-sheet content to decrease by 1.7%. In addition, NaCl enhanced the thermal stability of AlgM4 and increased the midpoint of thermal denaturation (Tm) by 4.9 °C. AlgM4 exhibited an ability to degrade sodium alginate, poly-mannuronic acid (polyM), and poly-guluronic acid (polyG), resulting in the production of oligosaccharides with a degree of polymerization (DP) of 2–9. AlgM4 possessed broader substrate, indicating that it is a bifunctional alginate lyase. Thus, AlgM4 is a novel salt-activated and bifunctional alginate lyase of the PL7 family with endolytic activity. View Full-Text
Keywords: Vibrio weizhoudaoensis; alginate lyase; PL7 family; salt-activated enzyme Vibrio weizhoudaoensis; alginate lyase; PL7 family; salt-activated enzyme
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Huang, G.; Wang, Q.; Lu, M.; Xu, C.; Li, F.; Zhang, R.; Liao, W.; Huang, S. AlgM4: A New Salt-Activated Alginate Lyase of the PL7 Family with Endolytic Activity. Mar. Drugs 2018, 16, 120.

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