Fine structure of SMG alginate fragment in the light of its degradation by alginate lyases of Pseudomonas sp

Biochemical Characterization and Degradation Pattern of a Unique pH-Stable PolyM-Specific Alginate Lyase from Newly Isolated Serratia marcescens NJ-07

Enzymatic preparation of alginate oligosaccharides with versatile bioactivities by alginate lyases has attracted increasing attention due to its featured characteristics, such as wild condition and specific products. In this study, AlgNJ-07, a novel polyM-specific alginate lyase with high specific activity and pH stability, has been purified from the newly isolated marine bacterium Serratia marcescens NJ-07. It has a molecular weight of approximately 25 kDa and exhibits the maximal activity of 2742.5 U/mg towards sodium alginate under 40 °C at pH 9.0. Additionally, AlgNJ-07 could retain more than 95% of its activity at pH range of 8.0–10.0, indicating it possesses excellent pH-stability. Moreover, it shows high activity and affinity towards polyM block and no activity to polyG block, which suggests that it is a strict polyM-specific alginate lyase. The degradation pattern of AlgNJ-07 has also been explored. The activity of AlgNJ-07 could be activated by NaCl with a low concentration (100–300 mM). It can be observed that AlgNJ-07 can recognize the trisaccharide as the minimal substrate and hydrolyze the trisaccharide into monosaccharide and disaccharide. The TLC and ESI-MS analysis indicate that it can hydrolyze substrates in a unique endolytic manner, producing not only oligosaccharides with Dp of 2–5 but also a large fraction of monosaccharide. Therefore, it may be a potent tool to produce alginate oligosaccharides with lower Dps (degree of polymerization).

ALGINATE LYASE: review of major sources and enzyme characteristics, structure-function analysis, biological roles, and applications

Alginate lyases, characterized as either mannuronate (EC 4.2.2.3) or guluronate lyases (EC 4.2.2.11), catalyze the degradation of alginate, a complex copolymer of alpha-L-guluronate and its C5 epimer beta-D-mannuronate. Lyases have been isolated from a wide range of organisms, including algae, marine invertebrates, and marine and terrestrial microorganisms. This review catalogs the major characteristics of these lyases, the methods for analyzing these enzymes, as well as their biological roles. Analysis of primary sequence data identifies some markedly conserved motifs that should help elucidate functional domains. Information about the three-dimensional structure of a mannuronate lyase from Sphingomonas sp., combined with various mutagenesis studies, has identified residues that are important for catalytic activity in several lyases. Characterization of alginate lyases will enhance and expand the use of these enzymes to engineer novel alginate polymers for applications in various industrial, agricultural, and medical fields. In this review, we explore both past and present applications of this important enzyme and discuss its future prospects.

L-guluronan-specific alginate lyase from a marine bacterium associated with Sargassum

The major extracellular alginate lyase activities secreted by a Gram-negative, facultative bacterium associated with actively growing Sargassum fluitans have been resolved an examined for substrate specificity. A fraction excluded from Sephadex G-75 was equally active toward (1----4)-beta-D-mannuronan, (1----4)-alpha-L-guluronan, and alginate with the formation of di- and tri-saccharides as apparent limit products and oligo-saccharides indicative of an endolytic mechanism. A second fraction which was included during G-75 filtration was inactive toward D-mannuronan and 4 times more active toward L-guluronan than native alginate. Proton magnetic resonance spectrometry identified the primary product of this enzyme as O-(4-deoxy-alpha-L-erythro-hex-4-enopyranosyluronic acid)-(1----4)-O-(alpha-L-gulopyranosyluronic acid)-(1----4)-O-alpha-L-gulopyranuronic acid. The L-guluronan-specific enzyme requires 0.5 M NaCl for maximal activity and has been purified as a monomeric protein having an apparent molecular mass of 38 kD and an approximate pI of 4.5. The predominant formation of trisaccharide over the course of a reaction showed a primarily exolytic mechanism, indicating an enzyme activity unique from any previously reported.

A study of the reaction catalysed by alginate lyase VI from the sea mollusc, Littorina sp

The molecular weight of polymeric alginic acid digested by alginate lyase (poly(1,4-beta-D-mannuronide) lyase, EC 4.2.2.3) was determined at various stages of the lysis. Low molecular weigh fragments were detected only after 60-100% lysis. Some high molecular weight fragments remained intact even after addition of a fresh aliquot of enzyme to the digest. The enzyme showed maximal activity at pH 5.6 in 0.05 M salt. Enzyme activity was stimulated by addition of 7.5 mM CaCl2 and 0.2 M NaCl, when the pH optimum was between 8 and 8.5. Only mannuronic acid was detected at the reducing end of fragments after exhausive enzymolysis, reduction and hydrolysis. On studying the reaction products by NMR, a double-bound signal (sigma = 5.98 ppm) was observed. A considerable decrease in intensity of the D-mannuronic acid residue signal was detected after hydrolysis of alginate lyase VI on poly-(ManUA-GulUA), but not poly(GulUA). The results suggest that alginate lyase VI may be an endoalginate lyase that splits glycoside bonds only between two mannuronic acid residues.