The assimilation of tri- and XXXX by @entity1 erythrocytes.

@entity1 @entity71417 @entity18847 @entity68854 @entity71418 @entity9881 @entity12274
Evidence is presented that @entity12274 enter @entity1 erythrocytes via saturable transport system(s) at rates similar to those previously described for @entity9881 (King, G.F. and Kuchel, P.W. (1985) Biochem. J. 227, 833-842) but that the transmembrane flux rates for @entity18847 are considerably less. 1H spin-echo NMR spectroscopy was used to monitor the coupled uptake and hydrolysis of peptides by red cells, since it enabled the simultaneous measurement of the levels of substrates and products of peptidase-catalysed reactions in suspensions with haematocrits similar to those found in vivo. Weighted non-linear least-squares regression of the integrated Michaelis-Menten equation onto progress curves obtained from the hydrolysis of @entity71417 and @entity68854 in RBC lysates gave Km = 2.11 +/- 0.08 and 23.4 +/- 0.9 mmol/l and Vmax = 307 +/- 3 and 905 +/- 22 mmol/h per 1 packed cells, respectively. In whole cell suspensions, the rate of hydrolysis was considerably less and was dominated by the transmembrane flux of @entity12274 . Progress curve analysis thus yielded the steady-state kinetic parameters for peptide transport; the values were Km = 11.6 +/- 1.1 and 56 +/- 18 mmol/l and Vmax = 12.9 +/- 3.0 and 36.4 +/- 3.2 mmol/h per 1 packed cells, respectively, for the previously mentioned peptides. The rate of transport of the tetrapeptide @entity71418 was considerably less than either of the @entity12274 . The above mentioned steady-state kinetic parameters were used in computer simulations of the coupled uptake and hydrolysis of @entity12274 by @entity1 erythrocytes under physiological conditions; these simulations revealed certain similarities between the rates of peptide uptake by erythrocytes and the intestine in vivo.
