[Nicotinamidase and the so-called pyrazinamidase in mycobacteria; the simultaneous occurrence of both activites (author's transl)].

: Nicotin- and the so-called pyrazinamidase (in the following: "pyrazinamidase") have been found in strains of four mycobacteria species, M. fortuitum, M. gastri, M. bovis and M. microti. These findings are in contradiction to those summarized in Bergey's Manual of Determinative Bacteriology (1974). The reason for the discrepancies is that the original method (Bonicke, 1961) for amidase determination has not taken the following aspects into consideration: a) The inducibility of the nicotin- and "pyrazinamidase" (example: M. fortuitum); b) The temperature sensitivity of these enzymes (M. gastri); c) The light sensitivity of nicotinamidase (in photochromogenic M. gastri strains); d) The optimal substrate concentration which must be at least 4 mM instead of 0,8 mm. The following consequences can be drawn for the taxonomy and biochemistry of the tested organisms: e) The species status of M. gastri should be annuled. The main difference between M. gastri and M. kansasii consists only of the non-agglutinability of M. gastri by anti-M. kansasii serum. "Pyrazinamidase" and also nitrate reductase (Tarnok et al., in press) are positive in strains of both species; f) M. bovis possesses nicotin- and "pyrazinamidase" as M. tuberculosis too. Thus, these two species are more closely related than suggested earlier; g) Till now, no Mycobacterium has been found showing nicotinamidase without "pyrazinamidase" activity (or vice versa). It seems to be very probable that nicotinamidase, an enzyme of low substrate specificity, is able to hydrolyze several compounds with a nicotinamide-like structure such as pyrazinamide. Thus, we suggest the annulment of the term pyrazinamidase or the employment of quotation marks ("pyrazinamidase") to show the fictitious value of this designation.