ABSTRACT
Phosphotransacetylase (Pta), a key enzyme in bacterial metabolism, catalyzes the reversible transfer of an acetyl group from acetyl phosphate to coenzyme A (CoA) to produce acetyl-CoA and P
i
. Two classes of Pta have been identified based on the absence (Pta
I
) or presence (Pta
II
) of an N-terminal regulatory domain. Pta
I
has been fairly well studied in bacteria and one genus of archaea; however, only the
Escherichia coli
and
Salmonella enterica
Pta
II
enzymes have been biochemically characterized, and they are allosterically regulated. Here, we describe the first biochemical and kinetic characterization of a eukaryotic Pta from the oomycete
Phytophthora ramorum
. The two Ptas from
P. ramorum
, designated PrPta
II
1 and PrPta
II
2, both belong to class II. PrPta
II
1 displayed positive cooperativity for both acetyl phosphate and CoA and is allosterically regulated. We compared the effects of different metabolites on PrPta
II
1 and the
S. enterica
Pta
II
and found that, although the N-terminal regulatory domains share only 19% identity, both enzymes are inhibited by ATP, NADP, NADH, phosphoenolpyruvate (PEP), and pyruvate in the acetyl-CoA/P
i
-forming direction but are differentially regulated by AMP. Phylogenetic analysis of bacterial, archaeal, and eukaryotic sequences identified four subtypes of Pta
II
based on the presence or absence of the P-loop and DRTGG subdomains within the N-terminal regulatory domain. Although the
E. coli
,
S. enterica
, and
P. ramorum
enzymes all belong to the IIa subclass, our kinetic analysis has indicated that enzymes within a subclass can still display differences in their allosteric regulation.
Characterization of distinct molecular interactions responsible for IRF3 and IRF7 phosphorylation and subsequent dimerization
