L'effet de la [formula omitted] et de l'inh sur l'activité catalasique des mycobactéries

Abstract

The catalase activity of mycobacteria as well as the purified catalase of beef liver are inhibited by d-cycloserine and also by isonicotinic acid hydrazide (INH), d-cycloserine inhibition being markedly stronger. In either case, inhibition can be reversed and has a noncompetitive character (substrate: H 2O 2). d-Cyclosine and INH are not specifically catalase inhibitors: they also block peroxidase (“horse radish”) in its purified form and the peroxidase activity of the TB bacilli, as well as a part of their respiration (probably the cytochrome-oxidase system). In contrast to the INH-resistant culture, whose catalase activity is zero, the cultures of TB bacilli resistant to d-cycloserine (and sensitive to INH) appear in no case to be devoid of catalase. The catalase activity of strains resistant to d-cycloserine (and sensitive to INH) may, according to the strains, be interchanged, slightly diminished (bovine strain Ravenel), or greatly augmented (human strains H 37Rv, H 37Ra) in comparison with that of control cultures. In the same strain (H 37Ra), in the presence of d-cycloserine, there is a marked increase in catalase activity in the proliferating stage of the bacteria (Kat. f. augmented by 50–60%), whereas in the non-proliferating stage there is no increase whatever (Kat. f. unchanged). A culture (H 37Rv) resistant to INH (devoid of catalase) and adapted subsequently to d-cycloserine does not recover any catalase activity.