[Asparagine metabolism in mycobacteria. II. -- Asparagine hydrolysis and aspartohydroxamic acid formation and hydrolysis catalysed by M. fortuitum, M. phlei and BCG asparaginases (author's transl)].

Crude extracts of BCG, M. fortuitum and M. phlei, hydrolyse asparagine (I) and L-beta-asparthohydroxamic acid (III), and catalyse the synthesis of aspartohydroxamic acid from asparagine and hydroxylamine (II). The ratio between these enzymatic activities (I:II and I:III) presents a certain stability during the different steps of purification of these mycobacteria asparaginases. In particular, M. fortuitum asparaginase has been purified 90 to 130-fold, with recovery of approximately 10%. Only the fractions of supernatants which have an asparaginase activity catalyse the formation of aspartohydroxamate from asparagine and hydroxylamine. Some differences between the asparaginases of these strains are described. Particularaly, in comparison to reaction I, their abilities to catalyse reactions II and III vary noticeably from one asparaginase to an other. The asparaginase of BCG catalyses very slightly in the reactions II and III and is more specific of L-asparagine hydrolysis than are the asparaginases of M. fortuitum and of M. phlei. Furthermore, in the case of M. phlei, p-chloromercuribenzoate (pCMB) inhibits very stronly the reactions I and III and slightly reaction II, whereas conversely, for M. fortuitum, pCMB does not inhibit reactions I and III but strongly inhibits reaction II. In the case of BCG, these three reactions are not inhibited by pCMB. Moreover, the asparaginases from these strains are more or less sensitive to the ionic strength of the buffer used.