ISSN:
1399-3054
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Biology
Notes:
The H+/PPi stoichiometry of the mitochondrial H+-PPiase from pea (Pisum sativum L.) stem was determined by two kinetic approaches, and compared with the H+/substrate stoichiometries of the mitochondrial H+-ATPase, and the vacuolar H+-PPiase and H+-ATPase. Using sub-mitochondrial particles or preparations enriched in vacuolar membranes, the rates of substrate-dependent H+-transport were evaluated: by a mathematical model, describing the time-course of H+-gradient (ΔpH) formation; or by determining the rate of H+-leakage following H+-pumping inhibition by EDTA at the steady-state ΔpH. When the H+-transport rates were divided by those of PPi or ATP hydrolysis, measured under identical conditions, apparent stoichiometries of ca 2 were determined for the mitochondrial H+-PPiase and H+-ATPase, and for the vacuolar H+-ATPase. The stoichiometry of the vacuolar H+-PPiase was found to be ca 1. From these results, it is suggested that the mitochondrial H+-PPiase may, in theory, function as a primary H+-pump poised towards synthesis of PPi and, therefore, acting in parallel with the main H+-ATPase.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1034/j.1399-3054.1998.1030302.x
Permalink