Reversible changes in the activity of inorganic pyrophosphatase of Streptococcus faecalis. The effect of compounds containing SH-groups.
The activity of inorganic pyrophosphatase (EC 3.6.1.1) from Streptococcus faecalis ATCC 8043 decreased rapidly, when the cell extracts prepared by lysozyme and osmotic shock were incubated in a buffer solution (pH 8.0) at 25-50 degrees C. Increase in pH (from 8.5 to 10.5) retarded the inactivation considerably. The low activity level was reached in 2.5 h at 37 degrees C (pH 8.0) and this residual activity was stable during prolonged incubation. The enzyme in the form of low activity was not rapidly denatured until at 70 degrees C. The inactivation could be prevented and reversed by cysteine, dithiotreitol and 2-mercaptoethanol, but reductants, which do not contain SH-groups were not effective. Reduced glutathione slowed down and oxidized glutathione stimulated the inactivation. With pure enzyme it was shown that the low, stable activity level obtained with crude extracts during incubation is a property of inorganic pyrophosphatase and not due to another enzyme with a low capacity to hydrolyze inorganic pyrophosphate. These findings suggest that inorganic pyrophosphatase form S. faecalis exists in two interconvertible forms which differ in activity.
D001431:Bacteriological Techniques; D003545:Cysteine / Q000494:pharmacology; D004229:Dithiothreitol / Q000494:pharmacology; D013293:Enterococcus faecalis / Q000201:enzymology*; D006863:Hydrogen-Ion Concentration; D008623:Mercaptoethanol / Q000494:pharmacology; D011755:Pyrophosphatases / Q000302:isolation & purification / Q000378:metabolism*; D013438:Sulfhydryl Compounds / Q000494:pharmacology*; D013696:Temperature
D013438:Sulfhydryl Compounds; D008623:Mercaptoethanol; D011755:Pyrophosphatases; D003545:Cysteine; D004229:Dithiothreitol