ISSN:
1432-072X
Keywords:
Adenylate kinase
;
ATP-AMP phosphotransferase
;
Enzyme regulation
;
Enzyme purification
;
Enzymology
;
Chemolithotrophy
;
Autotrophy
;
Thiobacilli
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract Adenylate kinase (ATP:AMP phosphotransferase, EC 2.7.4.3) from Thiobacillus novellus was purified 54-fold. The preparation was, on the basis of densitometer scans of polyacrylamide gels, at least 85% pure. The optimum pH in the forward direction (2 ADP ⇌ATP+AMP) was about 8.7, and in the reverse 8.2 The enzyme was specific for AMP, ADP and ATP with apparent K m values of 0.04, 0.34 and 0.09 mM respectively. A double reciprocal plot of specific activity vs. (ADP)2 was linear. Both AMP and ATP inhibited the forward reaction with AMP the more inhibitory of the two. AMP inhibition was competitive with respect to ADP with a K i of 0.125 mM. Although Mg2+ was necessary for maximal activity, about 20% of this was obtained in its absence. Co2+ and Mn2+ at similar concentrations gave 46% and 26% respectively of the activity found with Mg2+. Apparent K m for Mg2+ was about 0.054 mM in the forward and 0.15 mM in the reverse direction. pHMB and HgCl2 were potent inhibitors. Inhibition by pHMB but not HgCl2 was reversible by GSH or cysteine. Arrhenius plots gave an E a of 3.25 kcal/mole/degree C in the forward direction without discontinuity. In the reverse, there was a “break” at 26.7°C with an E a of 3.62 kcal/mole/degree C for lower temperatures and 3.92 kcal/mole/degree C for higher temperatures.Molecular weights of the enzyme were 46,300±300 by SDS PAGE and 47,800±200 by SDS PAGE after treatment with 5 M urea and about 40,000 by sucrose density gradient centrifugation.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00427738
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