Isomerization of a stable enzyme form does not affect the algebraic form of the rate equation in the absence of products, but product inhibition patterns are modified so that the order of addition of substrates and release of products can not be determined by steady-state kinetic experiments. Rate constants for steps involving the isomerizing stable form or any central complex are not determinable, and steady-state distributions can be calculated only for non-isomerizing [Pg.168]

If a stable enzyme form isomerizes, new terms appear in the denominator of the velocity equatioa The new denominator terms for several iso systems are summarized in Table 1. [Pg.169]

If a stable enzyme form isomerizes and these isomerization steps are a part of the reaction pathway, the term Iso is provided. For a Uni Uni mechanism in which an isomerization step occurs [e.g., the reaction sequence E -I- A EA EA FP FP F -I- P and F E] is designated an Iso Uni Uni scheme. If more than one isomerization event occurs, then the prefixes di-, tri-, etc, are utilized with Iso. Note that this aspect of the nomenclature does not refer to isomerization steps which may or may not occur between central complexes. [Pg.153]

The iso mechanisms, with isomerization of a stable enzyme form, are not very common in ordinary soluble enzyme systems. Well characterized examples of iso mechanisms are proline racemase, funiarase, and carbonic anhydrase (Rebholz Northrop, 1995). [Pg.169]

ISOMERIZATION OF TRANSITORY COMPLEXES AND STABLE ENZYME FORMS [Pg.168]

Isomerization of a transitory complex in any mechanism does not affect the form of the rate equation, but if a stable enzyme form isomerizes, additional terms occur in the denominator. [Pg.168]

Chance Bi Bi mechanism. (This expression also applies to isomerization mechanisms for the ordered and Theorell-Chance schemes in which a stable enzyme form undergoes isomerization.) The points of intersection for each different mechanism can be used to exclude certain possibilities, depending on the quality of the rate data. [Pg.564]

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