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Enzymatic degradation of L‐cysteine in human dental plaque
Author(s) -
PAUNIO ILKKA K.,
PAUNIO KEIJO U.
Publication year - 1971
Publication title -
european journal of oral sciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.802
H-Index - 93
eISSN - 1600-0722
pISSN - 0909-8836
DOI - 10.1111/j.1600-0722.1971.tb02029.x
Subject(s) - chemistry , cysteine , flavin mononucleotide , cofactor , enzyme , cystine , iodoacetamide , flavin adenine dinucleotide , biochemistry , chromatography
– Human dental plaque was collected into iced water. The starting crude enzyme preparation — obtained by sonication and ultracenfrifugation ‐ was tested for its keto acid‐forming activity using different amino acids as substrate. It could be shown that only L‐cystine and L‐cysteine were converted to keto acid by this enzyme preparation. The partly purified enzyme preparation, after BioGel P‐300 gel permeation chromatography, was capable of forming keto acid only from L‐cysteine. The affector studies conducted revealed that cations, such as Al 2+ , Cr 3+ , Ca 2+ , Fe 2+ , and Cu t+ , reduced the reaction velocity, and the same could be noted when Na‐cyanide, dithiotreitol, and mercapto‐ethanol were tested. NaF, MgCl 2 , iodoacetate, Na‐citrate, and Na 2 ‐EDTA exerted no effect on this enzymic reaction. The tested coenzymes, flavin mononucleotide (FMN), flavin dinucleotide (FAD), riboflavin phosphate, and pyridoxal‐5‐phosphate, were innocuous to the keto acid‐forming activity. This study confirms earlier studies that human dental plaque contains an enzyme disulfide reductase, an enzyme known to convert L‐cystine to L‐cysteine, and suggests the existence of a desulfhydrase enzyme in the plaque which converts L‐cysteine to pyruvic acid, ammonia, and hydrogen sulfide.