Synthetase, 5-dehydroquinic acid

TDP-streptose Biosynthesis and 5-Dehydroquinic Acid Synthetase The question mark in the above title should indicate that the next two examples are only a tempting, though hopefully constructive, speculation to demonstrate that TDP-streptose biosynthesis as well as 5-dehydro-quinic synthetase are possible candidates for this group of enzymes with identical initiation of enzyme catalysis by hydrogen transfer to form enzyme-NADH. 

Dehydroquinic acid synthetase ° Predicted, but not experimentally verified. 5 5 47... 

A working hypothesis to explain the activity of 5-dehydroquinate synthetase may be formulated as in Fig. 7. The hydroxyl group on C5 of 3-deoxy-D-orai tno-heptulosonic acid 7-phosphate is first oxidized by diphos-phop3uidine nucleotide, to facilitate the elimination of phosphate in the next step. The carbonyl group on C5 is then reduced (by the reduced di-phosphopjTidine nucleotide formed in the first reaction) to a hydroxyl group... 

In B. subtilis the single DAHPS enzyme is repressed most strongly by tyrosine, but maximal repression required the presence of both tyrosine and phenylalanine [121]. Tryptophan appeared to play no role in repression eontrol of synthesis of the enzyme. Nester et al. [121] also reported that a mixture of the three aromatic amino acids repressed synthesis of DAHPS, dehydroquinate synthetase, and shikimate kinase noncoordinately, but had no effect on the level of dehydroquinase. 

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