Celis Heliodoro, Franco Bernardo, Escobedo Silvia, Romero Irma
Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Apartado Postal 70-243, 04510, D.F. México, México.
Arch Microbiol. 2003 May;179(5):368-76. doi: 10.1007/s00203-003-0539-2. Epub 2003 Apr 1.
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.
对球形红杆菌的胞质焦磷酸酶进行了纯化和表征。该酶是一种64 kDa的同型二聚体。对其N端进行了测序，并用于从球形红杆菌的初步基因组序列中获得完整的焦磷酸酶序列，结果表明该序列与II类或C类焦磷酸酶具有广泛的序列相似性。该酶仅水解Mg-PP(i)和Mn-PP(i)，两种底物的K(m)均为0.35 mM。与深红螺菌的胞质焦磷酸酶不同，它不受游离Mg(2+)的激活，也不受NaF、亚甲基二磷酸或亚氨基二磷酸的抑制。这项研究表明，球形红杆菌和荚膜红杆菌的胞质焦磷酸酶属于II类，而深红螺菌、沼泽红假单胞菌、明胶红假单胞菌和万氏红微菌的胞质焦磷酸酶应归类为I类成员。这是光合细菌和革兰氏阴性生物中II类胞质焦磷酸酶的首次报道。
