title: Altered diaphorase activity in optochin-resistant pneumococci.
abstract: Methylene blue (MB) reductase activities of washed cell suspensions and of cell-free extracts prepared from optochin-resistant mutant pneumococci were two times greater than and four to eight times more resistant to optochin inhibition than those of similar preparations from the optochin-sensitive parent strains. With whole cells, optochin hydrochloride was approximately four times more potent than quinine hydrochloride in inhibiting MB reductase activity. However, with cell-free extracts, both drugs had similar inhibitory activities. Glucose uptake was not affected by optochin hydrochloride, and both optochin-sensitive and optochin-resistant pneumococci had similar glucose uptake patterns. Diaphorase activities of cell-free extracts prepared from optochin-resistant pneumococci were two times greater than and four to eight times more resistant to optochin inhibition than those of cell-free extracts prepared from the optochin-sensitive parent strains. Flavin concentrations of cell-free extracts prepared from optochin-sensitive and optochin-resistant strains were similar.
mesh_terms: D002474:Cell-Free System; D002929:Cinchona / Q000494:pharmacology*; D008058:Dihydrolipoamide Dehydrogenase / Q000378:metabolism*; D004352:Drug Resistance, Microbial; D005486:Flavin Mononucleotide / Q000378:metabolism; D005182:Flavin-Adenine Dinucleotide / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D008751:Methylene Blue / Q000378:metabolism; D009154:Mutation; D010946:Plants, Medicinal; D013296:Streptococcus pneumoniae / Q000187:drug effects* / Q000201:enzymology
chemical_list: D005182:Flavin-Adenine Dinucleotide; D005486:Flavin Mononucleotide; D008058:Dihydrolipoamide Dehydrogenase; D005947:Glucose; D008751:Methylene Blue