HPLC ANALYSIS OF SATURATED OR UNSATURATED OLIGOGULURONATES AND OLIGOMANNURONATES - APPLICATION TO THE DETERMINATION OF THE ACTION PATTERN OF HALIOTIS-TUBERCULATA ALGINATE LYASE

The chromatographic behaviour of various saturated and unsaturated oli gouronates obtained by acid or enzymatic degradation of homopolymeric blocks of alginates was investigated by isocratic anion exchange liqui d chromatography. This approach was then applied to the determination of the catalytic properties of Haliotis tuberculata alginate lyase. Th is enzyme presents a high affinity for poly-beta-D-mannuronate blocks, leading to the release of -(4-deoxy-alpha-L-erythro-hex-4-enopyranosy luronic acid)-(1 --> 4)-O-(beta-D-mannopyranosyluronic acid)-(1 --> 4) -O-beta-D-mannopyranuronic acid as the main end reaction product. Kine tic analysis with oligomannuronates of various sizes indicate that the catalytic site of Haliotis tuberculata lyase (abalone) best accommoda tes an oligomannuronate pentamer. The abalone lyase, however, is also capable of cleaving the G-M linkages of alginate heteropolymeric seque nces. In contrast, it does not degrade the G-G nor the M-G diads. This lyase should therefore be referred to as a mannuronate beta-eliminase , indicating that the enzyme performs beta-elimination on mannuronate residues only, from both the M-M and G-M diads of alginates. (C) 1996 Elsevier Science Ltd.