The uptake of alanine-14C by soybean root cells grown in sterile suspension culture

Abstract

A method has been adapted to follow quantitatively the uptake of L-alanine-14C, and presumably other 14C-labeled compounds, into soybean (Glycine max. cv. Mandarin) root cells growing in sterile suspension culture. Details are given of the growth and assay requirements needed to yield reproducible data.When alanine-14C uptake is followed into cells grown in the presence of nitrogen until immediately before assaying, a double reciprocal plot of velocity against alanine concentration yields a straight line which passes through zero, indicating that increasing substrate concentration will not saturate this uptake system. When cells are starved of nitrogen for 12 h before they are assayed, uptake rates increase by more than 100 times and a substrate-saturable uptake system can be detected. A Km value of 2.55 × 10−6 M was calculated. This saturable system is also strongly and rapidly affected by the respiratory inhibitors 2,4-dinitrophenol (DNP) and sodium azide.