In vitro and in vivo activation of L-serine deaminase in Escherichia coli K-12

Abstract

Escherichia coli L-serine deaminase (L-SD) in crude extracts made in glycylglycine could be activated by incubation with iron sulfate and dithiothreitol. This activation could also be demonstrated in vitro in two mutants which were physiologically deficient in L-SD activity in vivo. This suggests that these mutants were deficient not in L-SD but in an enzyme(s) activating L-SD. The suggestion is made that production of a functional L-SD in vivo requires activation of the structural gene product by an enzyme or enzymes that reduce the protein to an active form.

Deficiency in l‐serine deaminase results in abnormal growth and cell division of Escherichia coli K‐12

“…Similarly, if E. coli K12 lost its serine deaminase activity in some other way, one would expect it also to filament in LB. To test this, we took advantage of an 'activation' mutant MEW191 in which the L-SD1 molecule is made and can be activated in vitro (Newman et al, 1985) but no active L-SD can be made in vivo. This mutant is functionally a triple mutant as none of the three enzymes can be activated, and indeed this strain also filamented on subculture into LB.…”

L‐Serine and L‐threonine dehydratase from Clostridium propionicum Two enzymes with different prosthetic groups

“…Nevertheless, there would be a sufficient number of cysteinyl residues to complex at least one iron-sulfur cluster. In addition, L-serine dehydratase of E. coli is similarly activated by FeZ+ and dithiothreitol (Newman et al, 1985). Hence, there is ample reason to believe that the enzyme from E. coli might also be a member of the class of iron-sulfur-dependent enzymes.…”

“…These dehydratases are distinguished by their extreme instability and their ability to be protected, and in some cases activated, by substrate and/or competitive inhibitors (Alfoldi et al, 1968;Carter and Sagers, 1972;Morikawa et al, 1974;Gannon et al, 1977;Newman and Kapoor, 1980). Moreover, L-serine dehydratase from Clostridiuni acidi-urici (Carter and Sagers, 1972), E. coli (Newman et al, 1985). Lnctobacillus fermentum (Farias et al, 1991) and several other lactic acid bacteria (Farias et al, 1988) have been recognized to require activation by Fe".…”

Unusual dehydrations in anaerobic bacteria

“…Most probably, the enzyme is only the first known member of a whole family of iron-sulfur-dependent L-serine dehydratases. There is evidence that enzymes from C. acidi-urici [88], lactic acid bacteria [89], E. coli [90] and C. propionicum (A.E.M. Hofmeister and W. Buckel, unpublished) also contain iron-sulfur clusters.…”