Abstract
Glucose - induced arginine transport system was induced by a exogenous application of NH$_4$^+ ion. The uptake rate of arginine (Arg) depended on the external NH$_4$^+ ion concentration. The uptake rate was inhibited by the presence of NH$_4$^+ ion within 1 min, whereas it increased maximally after 30 min. Glucose and NH$_4$^+ ion induced the same arginine transport system. Km value of Arg transport systems was 2 $\mu$M, and V_(max) was 60 $\mu$mol^(-1) . h . g fresh weight^(-1) for NH$_4$^+ ion and 174 $\mu$mol^(-1) . h . g fresh weight^(-1) for glucose induced transport system. But, the transport system of Glu for glucose and NH$_4$^(-1) ion induced had different Km values. Km value of Glu was 285 $\mu$M for glucose - and 58 $\mu$M for NH$_4$^+ ion induced transport system. Thus, NH$_4$^+ ions play a important role as inducer for the glutamine transport system. NH$_4$^+ ion induced glutamine system was inhibited over 90% by cycloheximide. We concluded that a new carrier protein for glutamine was induced by NH$_4$^+ ion.