A New Class of Phosphotransferases Phosphorylated on an Aspartate Residue in an Amino-terminal DXDX(T/V) Motif
When incubated with their substrates, human phosphomannomutase and l-3-phosphoserine phosphatase are known to form phosphoenzymes with chemical characteristics of an acyl-phosphate. The phosphorylated residue in phosphomannomutase has now been identified by mass spectrometry after reduction of the p...
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Veröffentlicht in: | The Journal of biological chemistry 1998-06, Vol.273 (23), p.14107-14112 |
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Sprache: | eng |
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Zusammenfassung: | When incubated with their substrates, human phosphomannomutase and l-3-phosphoserine phosphatase are known to form phosphoenzymes with chemical characteristics of an acyl-phosphate. The phosphorylated residue in phosphomannomutase has now been identified by mass spectrometry after reduction of the phosphoenzyme with tritiated borohydride and trypsin digestion. It is the first aspartate in a conserved DVDGT motif. Replacement of either aspartate of this motif by asparagine or glutamate resulted in complete inactivation of the enzyme. The same mutations performed in the DXDST motif of l-3-phosphoserine phosphatase also resulted in complete inactivation of the enzyme, except for the replacement of the second aspartate by glutamate, which reduced the activity by only about 40%. This suggests that the first aspartate of the motif is also the phosphorylated residue inl-3-phosphoserine phosphatase. Data banks contained seven other phosphomutases or phosphatases sharing a similar, totally conserved DXDX(T/V) motif at their amino terminus. One of these (β-phosphoglucomutase) is shown to form a phosphoenzyme with the characteristics of an acyl-phosphate. In conclusion, phosphomannomutase and l-3-phosphoserine phosphatase belong to a new phosphotransferase family with an amino-terminal DXDX(T/V) motif that serves as an intermediate phosphoryl acceptor. |
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ISSN: | 0021-9258 1083-351X |
DOI: | 10.1074/jbc.273.23.14107 |