Sarafian V, Potier M, Poole R J
Department of Biology, McGill University, Montréal, Québec, Canada.
Biochem J. 1992 Apr 15;283 ( Pt 2)(Pt 2):493-7. doi: 10.1042/bj2830493.
The functional sizes of the vacuolar H(+)-ATPase (V-ATPase; EC 3.6.1.34) and H(+)-pyrophosphatase (PPase; EC 3.6.1.1) from vacuolar membranes of red beet (Beta vulgaris L.) were estimated by radiation inactivation, both for substrate hydrolysis and for H+ transport. For the V-ATPase, the radiation-inactivation size for H+ transport was 446 (403-497) kDa and that for ATP hydrolysis was 394 (359-435) kDa. The low values of both of these estimates suggest that not all subunits which may co-purify with V-ATPases are required for either hydrolysis or transport. For the PPase, the radiation-inactivation size for hydrolysis was 91 (82-103) kDa, suggesting that the minimum functional unit for hydrolysis is the 81 kDa monomer. In contrast to the V-ATPase, the PPase gave a radiation-inactivation size for transport which was 3-4-fold larger than that for hydrolysis (two estimates for transport gave 307 and 350 kDa), indicating that a single catalytic subunit is insufficient for transport activity.
通过辐射失活法，对红甜菜（Beta vulgaris L.）液泡膜上的液泡H(+)-ATP酶（V-ATP酶；EC 3.6.1.34）和H(+)-焦磷酸酶（PP酶；EC 3.6.1.1）的功能大小进行了估计，涉及底物水解和H+转运两个方面。对于V-ATP酶，H+转运的辐射失活大小为446（403 - 497）kDa，ATP水解的辐射失活大小为394（359 - 435）kDa。这两个估计值都较低，表明与V-ATP酶共纯化的所有亚基并非水解或转运所必需。对于PP酶，水解的辐射失活大小为91（82 - 103）kDa，这表明水解的最小功能单位是81 kDa的单体。与V-ATP酶不同，PP酶的转运辐射失活大小比水解的大3 - 4倍（两个转运估计值分别为307和350 kDa），这表明单个催化亚基不足以支持转运活性。
