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Journal of Bacteriology, September 2000, p. 4704-4710, Vol. 182, No. 17
Department of Oral Biochemistry, Tohoku
University School of Dentistry, 4-1 Seiryo-machi, Aoba-ku, Sendai,
980-8575, Japan
Received 13 March 2000/Accepted 25 May 2000
Metabolic pathways involved in the formation of cytotoxic end
products by Porphyromonas gingivalis were studied. The
washed cells of P. gingivalis ATCC 33277 utilized peptides
but not single amino acids. Since glutamate and aspartate
moieties in the peptides were consumed most intensively, a dipeptide of
glutamate or aspartate was then tested as a metabolic
substrate of P. gingivalis. P. gingivalis cells metabolized
glutamylglutamate to butyrate, propionate, acetate, and ammonia,
and they metabolized aspartylaspartate to butyrate, succinate,
acetate, and ammonia. Based on the detection of metabolic enzymes in
the cell extracts and stoichiometric calculations (carbon recovery and
oxidation/reduction ratio) during dipeptide degradation, the
following metabolic pathways were proposed. Incorporated glutamylglutamate and aspartylaspartate are hydrolyzed to
glutamate and aspartate, respectively, by dipeptidase. Glutamate is
deaminated and oxidized to succinyl-coenzyme A (CoA) by glutamate
dehydrogenase and 2-oxoglutarate oxidoreductase. Aspartate is
deaminated into fumarate by aspartate ammonia-lyase and then reduced to
succinyl-CoA by fumarate reductase and acyl-CoA:acetate
CoA-transferase or oxidized to acetyl-CoA by a sequential reaction of
fumarase, malate dehydrogenase, oxaloacetate decarboxylase, and
pyruvate oxidoreductase. The succinyl-CoA is reduced to butyryl-CoA by
a series of enzymes, including succinate-semialdehyde dehydrogenase,
4-hydroxybutyrate dehydrogenase, and butyryl-CoA oxidoreductase. A part
of succinyl-CoA could be converted to propionyl-CoA through the
reactions initiated by methylmalonyl-CoA mutase. The butyryl- and
propionyl-CoAs thus formed could then be converted into acetyl-CoA by
acyl-CoA:acetate CoA-transferase with the formation of corresponding
cytotoxic end products, butyrate and propionate. The formed acetyl-CoA
could then be metabolized further to acetate.
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Metabolic Pathways for Cytotoxic End Product
Formation from Glutamate- and Aspartate-Containing Peptides by
Porphyromonas gingivalis
*
Corresponding author. Mailing address: Department of
Oral Biochemistry, Tohoku University School of Dentistry, 4-1 Seiryo-machi, Aoba-ku, Sendai, 980-8575, Japan. Phone: 81-22-717-8295. Fax: 81-22-717-8297. E-mail:
nobu-t{at}mail.cc.tohoku.ac.jp.
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