Miscellaneous enzymes

Although the tryptophan synthetase and tryptophanase reactions have been the best studied replacement and 0 eUmination-deamination reactions, others pf special interest are D-serine dehydratase [75-77] from E. coli, D-threonine dehydratase and L-threonine dehydratase from Serratia marcescens [78]. The only information available on the above enzymes is that in these cases also, the events at occur with retention of configuration. 

An unusual variant of a /8 elimination reaction is shown by kyneurinase which catalyses the production of L-alanine and 3-hydroxyanthranilate from 3-hydroxy kyneurine (Fig. 33), an intermediate in tryptophan biosynthesis. Although the reaction has not been subjected to mechanistic investigation a pathway consistent with the previously demonstrated properties of pyridoxal-P to stabilise a j8-carban-ion is illustrated in Fig. 34. 

X Medium Substrate configuration Enzyme Steric course at Cp 

HO- HjO (25,3/ )-[3- HJSerine (2 5,35 )-[3- HJSerine Tyrosine phenol lyase Retention [200J 

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Therapeutic enzymes have a broad variety of specific uses, ie, as oncolytics, thrombolytics, or replacements for inherited deficiencies. Additionally, there is a growing group of miscellaneous enzymes of diverse function. 

Miscellaneous (Enzymes, Amino Acids and Peptides, Plant Metabolites, Marine, Cyclodextrins, Other). 

The effect of thyroxine on a number of individual enzyme systems has also been investigated with the hope that the hormone s mechanism of action might be clarified. Studies have been done on four classes of enzymes phosphatases, dehydrogenases, transhy-drogenases, and miscellaneous enzymes. 

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