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Mise en évidence et propriétés de deux formes de la 5-déshydroquinate hydro-lyase chez les végétaux supérieurs

✍ Scribed by Alain M. Boudet; Raymond Lécussan; Annie Boudet

Publisher
Springer-Verlag
Year
1975
Tongue
English
Weight
561 KB
Volume
124
Category
Article
ISSN
0032-0935

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✦ Synopsis

Two dehydroquinate hydro-lyases (E.C. 4.2.1.10) have been routinely separated from different organs of Zea mays L. by chromatography on Cellex-D Bio-Rad or hydroxypatite using linear salt gradients. Dehydroquinate hydro-lyase 1 is associated with shikimate: NADP + oxidoreductase (E.C. 1.1.1.25). DHQase 2 is a free constitutive enzyme; in this respect it differs from the inducible enzyme of microorganisms which appears only when dehydroquinate or quinate is the principal carbon source. DHQase 1 and DHQase 2 have a similar apparent Michaelis constant and pH optimum, but they differ in their molecular weight, thermal stability and sensitivity to metabolic effectors. DHQase 2 is specifically activated by shikimie acid. This strong activation and the channeling properties of the complex involved in the shikimate pathway can provide an effective means of control in the utilization of dehydroquinate between two different pathways. The significance of such a system involving both a specific regulation of isoenzymes and a molecular compartmentation by means of an enzymatic complex is discussed.

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