Agarases are the enzymes which catalyze the hydrolysis of agar. They are classified into α-agarase (E.C. 3.2.1.158) and β-agarase (E.C. 3.2.1.81) according to the cleavage pattern. Several agarases have been isolated from different genera of bacteria found in seawater and marine sediments, as well as engineered microorganisms. Agarases have wide applications in food industry, cosmetics, and medical fields because they produce oligosaccharides with remarkable activities. They are also used as a tool enzyme for biological, physiological, and cytological studies. The paper reviews the category, source, purification method, major characteristics, and application fields of these native and gene cloned agarases in the past, present, and future.

An extracellular beta-agarase (AgaA34) was purified from a newly isolated marine bacterium, Agarivorans albus YKW-34 from the gut of a turban shell. AgaA34 was purified to homogeneity by ion exchange and gel filtration chromatographies with a recovery of 30% and a fold of ten. AgaA34 was composed of a single polypeptide chain with the molecular mass of 50 kDa. N-terminal amino acid sequencing revealed a sequence of ASLVTSFEEA, which exhibited a high similarity (90%) with those of agarases from glycoside hydrolase family 50. The pH and temperature optima of AgaA34 were pH 8.0 and 40 degrees C, respectively. It was stable over pH 6.0-11.0 and at temperature up to 50 degrees C. Hydrolysis of agarose by AgaA34 produced neoagarobiose (75 mol%) and neoagarotetraose (25 mol%), whose structures were identified by matrix-assisted laser desorption ionization time-of-flight mass spectroscopy and (13)C NMR. AgaA34 cleaved both neoagarohexaose and neoagarotetraose into neoagarobiose. The k (cat)/K (m) values for hydrolysis agarose and neoagarotetraose were 4.04 x 10(3) and 8.1 x 10(2) s(-1) M(-1), respectively. AgaA34 was resistant to denaturing reagents (sodium dodecyl sulfate and urea). Metal ions were not required for its activity, while reducing reagents (beta-Me and dithiothreitol, DTT) increased its activity by 30%.

A bromophenol, bis(2,3-dibromo-4,5-dihydroxybenzyl) ether, was purified from the red alga Polyopes lancifolia. Its IC(50) values were 0.098 and 0.120 microM against Saccharomyces cerevisiae and Bacillus stearothermophilus alpha-glucosidases, respectively, and 1.00 and 1.20 mM against rat-intestinal sucrase and maltase. This bromophenol competitively inhibited S. cerevisiae alpha-glucosidase with a K(I) value of 0.068 microM and was very stable at pH 2 for 60 min at 37 degrees C. Therefore, this P. lancifolia bromophenol may have potential as natural nutraceutical for the management of type 2 diabetes.

Violaxanthin is a major carotenoid of microalgae Chlorella ellipsoidea and is also found in dark-green leafy vegetables, such as spinach. In this study, the anti-inflammatory effect of violaxanthin isolated from C. ellipsoidea was examined using lipopolysaccharide (LPS)-stimulated RAW 264.7 mouse macrophage cells. In addition, the anti-inflammatory activity and mechanism of action of purified violaxanthin was assessed using various assays, such as quantitative real-time polymerase chain reaction (PCR), Western blotting, and electrophoretic-mobility shift assay (EMSA). The results of this combined analysis revealed that violaxanthin significantly inhibited nitric oxide (NO) and the prostaglandin E 2 (PGE 2 ). Interestingly, violaxanthin effectively inhibited LPS-mediated nuclear factor-κB (NF-κB) p65 subunit translocation into the nucleus, suggesting that the violaxanthin anti-inflammatory activity may be based on inhibition of the NF-κB pathways. In conclusion, violaxanthin of C. ellipsoidea holds promise for use as a potential anti-inflammatory agent for either therapeutic or functional adjuvant purposes.

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