The kinetics of glutamine transport in bovine lymphocytes

The transport of glutamine was examined in bovine peripheral lymphocytes which had been cultured in the presence or absence of Concanavalin A (Con A). Glutamine transport was mediated by a triphasic transport system in both cell populations. The calculated kinetic parameters were: Km 1.0, 4.7 and 12.7 mM and Vmax 4.5, 6.0 and 9.0 nmol/min per mg protein respectively. Con A augmented the capacity rather than the affinity of the glutamine transport systems (Vmax rates being 8.0, 12.2 and 38.0 nmol/min per mg protein respectively). Transporter I displayed Michaelis-Menton kinetics, while transporters II and III were co-operative carriers possessing Hill coefficients of 2.3 and 9.5 respectively. Preliminary studies using amino acid and ion inhibition studies suggested that transporter I was a system ASC-type carrier, transporter III a system L carrier, while the nature of transporter II was unclear.