Hymenolepis diminuta: The non-saturable component of methionine uptake |
| |
Authors: | P.E. Lussier R.B. Podesta D.F. Mettrick |
| |
Affiliation: | Department of Zoology, University of Toronto, Toronto, Ontario M5S 1A1, Canada |
| |
Abstract: | Lussier P. E., Podesta R. B. and Mettrick D. F. 1982. Hymenolepis diminuta: the non-saturable component of methionine uptake. International Journal for Parasitoiogy12: 265–270. The concentration dependence of in vitro unidirectional methionine influx by Hymenolepis diminuta was analysed by the relation: , where Jm is the maximum uptake rate, Kt is the the apparent affinity constant and Cb is the medium substrate concentration. The linear component was separated using an asymptotic least squares curve fitting procedure and the resulting constant, Kd, is thought to be an apparent permeability coefficient. Kd may be a reflection of a simple diffusive component, a second mediated component or a combination of a passive and mediated influx. The low Q10 value of the Kd's for methionine uptake (Q10 = 1.31) indicated that this component is probably a reflection of diffusion within the membrane. However, the decrease in the Kd component in the presence of leucine and glycine, implies that there is also a small, second, mediated component in addition to the diffusive component. Kd derived from the asymptotic portion of the concentration-flux relation was compared with the residual flux of methionine after near complete inhibition of the mediated component with leucine and glycine. The Kd component was found to be pH-sensitive, increasing as the pH decreased and was not affected by external sodium. Results indicate that the mediated component of methionine influx was accelerated by increasing external Na+ and H+ concentrations. |
| |
Keywords: | Methionine amino acid transport inhibitors apparent permeability coefficient |
本文献已被 ScienceDirect 等数据库收录! |
|