Cooperative manganese (II) activation of 3-phosphoglycerate mutase of Bacillus megaterium: a biological pH-sensing mechanism in bacterial spore formation and germination.
The conversion of 3-P-glycerate mutase of Bacillus megaterium from a catalytically inactive to an active form was markedly more effective with buffered Mn2+ than with just added Mn2+. The previously reported stimulation by threonine disappeared when buffered Mn2+ was used. Activation of mutase showed a sigmoid dependence on Mn2+ concentration when buffered with tetramethylenediamine tetraacetate. The curve obeyed Hill kinetics with a coefficient of 2.1 +/- 0.1. At 0.5 microM free Mn2+, buffered with trimethylenediamine tetraacetate, activation of mutase increased about 73-fold over the pH range 6.6 to 7.4. Plotted against [OH-], the activation showed a strongly sigmoid response with Hill coefficient of 3.5 +/- 0.1. When mutase activated at pH 6.4 and 0.5 microM free Mn2+ in the presence of substrate was transferred to a similar medium at pH 7.4, the rate of product accumulation increased 360-fold within a few minutes. The pH sensitivity conferred upon mutase by low [Mn2+] may account for its large activity decrease during sporulation, and later increase during spore germination, when spore pH, respectively, declines and rises by about 1 unit. These changes result in the accumulation, and later reutilization, of 3-P-glycerate reserves in the spore. Such a pH-sensing function of Mn2+ may have wider biological uses.
Kuhn
N J
NJ
School of Biochemistry, University of Birmingham, United Kingdom.
Setlow
B
B
Setlow
P
P
Cammack
R
R
Williams
R
R
D001410:Bacillus megaterium / Q000187:drug effects / Q000201:enzymology* / Q000502:physiology; D002021:Buffers; D004789:Enzyme Activation / Q000187:drug effects; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008345:Manganese / Q000494:pharmacology*; D008954:Models, Biological; D010736:Phosphoglycerate Mutase / Q000378:metabolism*; D012996:Solutions; D013171:Spores, Bacterial / Q000201:enzymology / Q000502:physiology
D002021:Buffers; D012996:Solutions; D008345:Manganese; D010736:Phosphoglycerate Mutase