scholarly journals Bulgecin A: a novel inhibitor of binuclear metallo-β-lactamases

2005 ◽  
Vol 387 (3) ◽  
pp. 585-590 ◽  
Author(s):  
Alan M. SIMM ◽  
E. Joel LOVERIDGE ◽  
John CROSBY ◽  
Matthew B. AVISON ◽  
Timothy R. WALSH ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Steady State ◽  
Stenotrophomonas Maltophilia ◽  
Competitive Inhibition ◽  
Zinc Ion ◽  
Glycosidic Linkage ◽  
Sugar Moiety ◽  
Aeromonas Veronii ◽  
Steady State Kinetic ◽  
State Kinetic

Bulgecin A, a sulphonated N-acetyl-D-glucosamine unit linked to a 4-hydroxy-5-hydroxymethylproline ring by a β-glycosidic linkage, is a novel type of inhibitor for binuclear metallo-β-lactamases. Using steady-state kinetic analysis with nitrocefin as the β-lactam substrate, bulgecin A competitively inhibited the metallo-β-lactamase BceII from Bacillus cereus in its two-zinc form, but failed to inhibit when the enzyme was in the single-zinc form. The competitive inhibition was restored by restoring the second zinc ion. The single-zinc metallo-β-lactamase from Aeromonas veronii bv. sobria, ImiS, was not inhibited by bulgecin A. The tetrameric L1 metallo-β-lactamase from Stenotrophomonas maltophilia was subject to partial non-competitive inhibition, which is consistent with a kinetic model in which the enzyme bound to inhibitor retains catalytic activity. Docking experiments support the conclusion that bulgecin A co-ordinates to the zinc II site in metallo-β-lactamases via the terminal sulphonate group on the sugar moiety.

scholarly journals Formation and properties of flavoprotein-cytochrome hybrids by recombination of subunits from different species

1985 ◽  
Vol 231 (2) ◽  
pp. 383-387 ◽  
Author(s):  
S C Koerber ◽  
D J Hopper ◽  
W S McIntire ◽  
T P Singer
Keyword(s):  
Catalytic Activity ◽  
Steady State ◽  
Isoelectric Focusing ◽  
Dissociation Constants ◽  
The Other ◽  
High Dilution ◽  
Steady State Kinetic ◽  
Isoelectric Points ◽  
State Kinetic ◽  
Enzyme Species

p-Cresol methylhydroxylases from four different pseudomonads differ in their isoelectric points and, to a lesser extent, in Mr values and substrate specificity. The enzymes from three species were isolated in homogeneous form, then resolved into their flavoprotein and cytochrome subunits, and the subunits were recombined to yield the nine possible hybrids (i.e. three intraspecies and six interspecies). The resulting flavocytochromes showed extensive similarities in steady-state kinetic parameters and in the dissociation constants of their subunits. Evidence is also presented that a fourth type of p-cresol methylhydroxylase, from Pseudomonas putida (N.C.I.B. 9869, form ‘B’), the subunits of which cannot be isolated by the isoelectric focusing technique used to separate the subunits of the other flavocytochromes, nevertheless dissociates slowly at high dilution. The dissociation is reflected by a decline of catalytic activity with time. This process for the ‘B’ enzyme is prevented by the presence of substrate or an excess of a cytochrome subunit isolated from another enzyme species. Incubation of the dissociated subunits with p-cresol brings about extensive, albeit incomplete, re-association and regeneration of activity.

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