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J. Bacteriol., Jan 1998, 119-127, Vol 180, No. 1
PS Subramaniam, G Xie, T Xia and RA Jensen
3-Deoxy-D-manno-octulosonate 8-phosphate (KDOP) synthase and 3-deoxy-D-
arabino-heptulosonate 7-phosphate (DAHP) synthase catalyze similar
phosphoenolpyruvate-utilizing reactions. The genome of Neisseria
gonorrhoeae contains one gene encoding KDOP synthase and one gene encoding
DAHP synthase. Of the two nonhomologous DAHP synthase families known, the
N. gonorrhoeae protein belongs to the family I assemblage. KDOP synthase
exhibited an ability to replace arabinose-5-P with either erythrose-4-P or
ribose-5-P as alternative substrates. The results of periodate oxidation
studies suggested that the product formed by KDOP synthase with
erythrose-4-P as the substrate was 3-deoxy-D-ribo- heptulosonate 7-P, an
isomer of DAHP. As expected, this product was not utilized as a substrate
by dehydroquinate synthase. The significance of the ability of KDOP
synthase to substitute erythrose-4-P for arabinose- 5-P is (i) recognition
of the possibility that the KDOP synthase might otherwise be mistaken for a
species of DAHP synthase and (ii) the possibility that the
broad-specificity type of KDOP synthase might be a relatively vulnerable
target for antimicrobial agents which mimic the normal substrates. An
analysis of sequences in the database indicates that the family I group of
DAHP synthase has a previously unrecognized membership which includes the
KDOP synthases. The KDOP synthases fall into a subfamily grouping which
includes a small group of DAHP synthases. Thus, family I DAHP synthases
separate into two subfamilies, one of which includes the KDOP synthases.
The two subfamilies appear to have diverged prior to the acquisition of
allosteric-control mechanisms for DAHP synthases. These allosteric control
specificities are highly diverse and correlate with the presence of
N-terminal extensions which lack homology with one another.
Copyright © 1998, American Society for Microbiology
Substrate ambiguity of 3-deoxy-D-manno-octulosonate 8-phosphate synthase from Neisseria gonorrhoeae in the context of its membership in a protein family containing a subset of 3-deoxy-D-arabino-heptulosonate 7-phosphate synthases [In Process Citation]
Department of Microbiology and Cell Science, University of Florida, Gainesville 32611, USA.
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