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.

scholarly journals Computer program for the kinetic equations of enzyme reactions. The case in which more than one enzyme species is present at the onset of the reaction

1991 ◽  
Vol 278 (1) ◽  
pp. 91-97 ◽  
Author(s):  
R Varón ◽  
B H Havsteen ◽  
M García ◽  
F García-Canóvas ◽  
J Tudela
Keyword(s):  
Steady State ◽  
Computer Program ◽  
Enzyme System ◽  
Kinetic Equations ◽  
British Library ◽  
Transient Phase ◽  
Enzyme Reactions ◽  
Steady State Kinetic ◽  
State Kinetic ◽  
Enzyme Species

This paper presents an extension of the program developed by Varón, Havsteen, García, García-Cánovas & Tudela [(1990) Biochem. J. 270, 825-828] for the expression of the transient-phase and steady-state kinetic equations of a general enzyme system in which the only enzyme species present at the onset of the reaction is the free enzyme. The program has been extended to situations in which more than one enzyme species may be present at the onset of the reaction. The program is given in Supplementary Publication SUP50165 (5 pages), which has been deposited at the British Library Document Supply Centre, Boston Spa, Wetherby, West Yorkshire LS23 7BQ, U.K., from whom copies can be obtained on the terms indicated in Biochem. J. (1991) 273, 5.

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.

Isoelectric focusing of insulin, 125I-insulin and the 125I-insulin-antibody complex

1979 ◽  
Vol 44 (6) ◽  
pp. 1828-1834
Author(s):  
Asja Šiševa ◽  
Jiřina Slaninová ◽  
Tomislav Barth ◽  
Stephan P. Ditzov ◽  
Luben M. Sirakov
Keyword(s):  
Isoelectric Focusing ◽  
Polyacrylamide Gel ◽  
The Other ◽  
Insulin Antibody ◽  
Isoelectric Points ◽  
Antibody Complex ◽  
And Storage ◽  
Acid Region ◽  
Three Components

Isoelectric focusing on polyacrylamide gel columns of three native crystalline commercial preparations of insulin and 125I-labelled insulin was carried out. All the compounds studied contained three components of different isoelectric points. The largest fraction, having pI 5.60 ± 0.05, was common to all preparations. The other two fractions were situated in the acid region of pH between pI 4.5 and 5.2. The presence of these fractions is explained by the contamination of crystalline insulins by proinsulin and by the formation of des-amido derivatives during the dissolving and storage of insulin samples, and, in case of labelled insulin, also by the presence of heavily iodinated insulin and contaminating components. The isoelectric focusing of the complex 125I-insulin-antibody showed a peak of radioactivity having pI 6.15 ± 0.05.

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