Catalytic mechanism of the phospholipase D superfamily proceeds via a covalent phosphohistidine intermediate.
Proc Natl Acad Sci U S A
; 95(16): 9202-7, 1998 Aug 04.
Article
em En
| MEDLINE
| ID: mdl-9689058
ABSTRACT
The phospholipase D (PLD) superfamily includes enzymes of phospholipid metabolism, nucleases, as well as ORFs of unknown function in viruses and pathogenic bacteria. These enzymes are characterized by the invariant sequence motif, H(X)K(X)4D. The endonuclease member Nuc of the PLD family was over-expressed in bacteria and purified to homogeneity. Mutation of the conserved histidine to an asparagine in the endonuclease reduced the kcat for hydrolysis by a factor of 10(5), suggesting that the histidine residue plays a key role in catalysis. In addition to catalyzing hydrolysis, a number of phosphohydrolases will catalyze a phosphate (oxygen)-water exchange reaction. We have taken advantage of this observation and demonstrate that a 32P-labeled protein could be trapped when the enzyme was incubated with 32P-labeled inorganic phosphate. The phosphoenzyme intermediate was stable in 1 M NaOH and labile in 1 M HCl and 1 M hydroxylamine, suggesting that the enzyme forms a phosphohistidine intermediate. The pH-stability profile of the phosphoenzyme intermediate was consistent with phosphohistidine and the only radioactive amino acid found after alkaline hydrolysis was phosphohistidine. These results suggest that the enzymes in the PLD superfamily use the conserved histidine for nucleophilic attack on the substrate phosphorus atom and most likely proceed via a common two-step catalytic mechanism.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Fosfolipase D
/
Histidina
Limite:
Humans
Idioma:
En
Revista:
Proc Natl Acad Sci U S A
Ano de publicação:
1998
Tipo de documento:
Article
País de afiliação:
Estados Unidos