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Coenzyme Saturation of Transaminases

It seems likely that it is normeil for a proportion of pyiidoxtd phosphate-dependent enzymes to be present as inactive apoenzyme, without coenzyme. This may be a mechanism of metabolic regulation. It is possible that incretising the intake of vitamin Be, to ensure complete saturation of pyiidoxtd phosphate-dependent enzymes, may not be desirable. [Pg.252]

A number of studies have measured the activation of plasma transaminases by pyridoxal phosphate added in vitro however, it is difficult to interpret the results, because plasma transaminases arise largely accidentally, as a result of cell turnover, and the amount released will depend on tissue damage. Furthermore, there is a considerable amount of pyridoxal phosphate in plasma, largely associated with serum albumin, and the extent to which plasma transaminases are saturated will depend largely on the relative affinity of albumin and the enzyme concerned for the coenzyme, rather than reflecting the availability of pyridoxal phosphate for intracellular metabolism. Studies on erythrocyte transaminase activation coefficient are easier to interpret, because the extent to which the enzymes are saturated depends mainly on the availability of pyridoxal phosphate. [Pg.252]


Various pyridoxal phosphate dependent enzymes compete with each other for the available pool of coenzyme. Thus the extent to which an enzyme is saturated with its coenzyme provides a means of assessing the adequacy of the body pool of coenzyme. This can be determined by measuring the activity of the enzyme before and after the activation of any apoenzyme present in the sample by incubation with pyridoxal phosphate added in vitro. Erythrocyte aspartate and alanine transaminases are both commonly used the results are usually expressed as an activation coefficient— the ratio of activity with added coenzyme to that without. [Pg.451]


See other pages where Coenzyme Saturation of Transaminases is mentioned: [Pg.252]    [Pg.252]    [Pg.252]    [Pg.252]    [Pg.252]    [Pg.252]    [Pg.20]    [Pg.252]    [Pg.252]    [Pg.243]   


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Of coenzyme

Transaminases

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