Rhodobacter sphaeroides has a family II pyrophosphatase: comparison with other species of photosynthetic bacteria.
The cytoplasmic pyrophosphatase from Rhodobacter sphaeroides was purified and characterized. The enzyme is a homodimer of 64 kDa. The N-terminus was sequenced and used to obtain the complete pyrophosphatase sequence from the preliminary genome sequence of Rba. sphaeroides, showing extensive sequence similarity to family II or class C pyrophosphatases. The enzyme hydrolyzes only Mg-PP(i) and Mn-PP(i) with a K(m) of 0.35 mM for both substrates. It is not activated by free Mg (2+), in contrast to the cytoplasmic pyrophosphatase from Rhodospirillum rubrum, and it is not inhibited by NaF, methylendiphosphate, or imidodiphosphate. This work shows that Rba. sphaeroides and Rhodobacter capsulatus cytoplasmic pyrophosphatases belong to family II, in contrast to Rsp. rubrum, Rhodopseudomonas palustris, Rhodopseudomonas gelatinosa, and Rhodomicrobium vannielii cytoplasmic pyrophosphatases which should be classified as members of family I. This is the first report of family II cytoplasmic pyrophosphatases in photosynthetic bacteria and in a gram-negative organism.
Celis
Heliodoro
H
Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Apartado Postal 70-243, 04510, D.F. México, México. hcelis@ifisiol.unam.mx
Franco
Bernardo
B
Escobedo
Silvia
S
Romero
Irma
I
D020561:Alphaproteobacteria / Q000201:enzymology; D000595:Amino Acid Sequence; D001483:Base Sequence; D002413:Cations, Divalent / Q000378:metabolism; D000458:Cyanobacteria / Q000145:classification / Q000235:genetics; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D008970:Molecular Weight; D011755:Pyrophosphatases / Q000737:chemistry / Q000145:classification / Q000302:isolation & purification / Q000378:metabolism*; D012242:Rhodobacter sphaeroides / Q000166:cytology / Q000201:enzymology* / Q000378:metabolism; D016415:Sequence Alignment; D012969:Sodium Fluoride / Q000378:metabolism; D013379:Substrate Specificity
D002413:Cations, Divalent; D012969:Sodium Fluoride; D011755:Pyrophosphatases