Catalytic properties and specificity of a recombinant, overexpressed D-mannuronate lyase.
Carbohydr Res
; 308(3-4): 409-15, 1998 Jun.
Article
em En
| MEDLINE
| ID: mdl-11001631
ABSTRACT
Lysis of alginates and of their saturated and unsaturated fragments was monitored by 1H NMR spectroscopy. AlxM(B) alginate lyase performs beta-elimination on the mannuronic acid (M) residues. It does not cleave the guluronic acid (G) sequences, nor the M-G or the G-M diads. In consequence, it is a true mannuronate lyase. The end product of the reaction is O-(4-deoxy-alpha-L-ery-thro-hex-4-enopyranosyl-uronic acid)-(1->(4)-O-(beta-D-mannopyranosyluronic acid)-(1->4)-O-beta-D-mannpyranuronic acid. Viscosity measurements made during degradation of a polymannuronate alginate showed that AlxM(B) behaves as an endo-enzyme. HPLC analysis of the degradation products of oligomannuronates and oligoalginates suggested that the beta-elimination requires the interaction of the enzyme with at least three sequential mannuronic acid residues. The catalytic site may possess 5 sub-sites and accommodate pentamers with different M/G ratio. Kinetic measurements showed that the specificity constant Vm/Km increased with the number of mannuronic acid residues. AlxM(B) may be reversibly inhibited by heteropolymeric blocks in a competitive manner.
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Base de dados:
MEDLINE
Assunto principal:
Polissacarídeo-Liases
Idioma:
En
Ano de publicação:
1998
Tipo de documento:
Article