Transport of glucose, fructose and sucrose byStreptanthus tortuosussuspension cells

✍ Scribed by Manfred Stanzel; Richard D. Sjolund; Ewald Komor

• Publisher: Springer-Verlag
• Year: 1988
• Tongue: English
• Weight: 819 KB
• Volume: 174
• Category: Article
• ISSN: 0032-0935
• DOI: 10.1007/bf00394772

✦ Synopsis

Streptanthus tortuosus Kell. suspension cells will grow in a medium with sucrose as carbohydrate source. It was investigated whether the cells are able to take up sucrose or whether sucrose has to be hydrolyzed to glucose and fructose which eventually are taken up. The detailed quantitative analysis of sugar-uptake rates in the low concentration range up to 1 mM showed the following features: (i)There is definitely no sucrose-uptake system working in the low concentration range; any uptake of radioactivity from labelled sucrose proceeds via hydrolysis of sucrose by cell-wallbound invertase. (ii) Hexoses are taken up by two systems, a glucose-specific system with a K m of 45 laM and a high Vmax for glucose and a K m of 6 mM and a low Vma~ for fructose, and a fructosespecific system with a K,~ of 500 ~tM and high a Vmax for fructose and a Km of 650 laM and a low //max for glucose. (iii) There is a more than tenfold preference for uptake of the fructose derived from sucrose versus uptake of free fructose, with the result that the kinetic disadvantage of the fructoseuptake system compared to the glucose-uptake system is diminished if sucrose is supplied as the carbon source. It is speculated that invertase might work as an enzyme aiding in fructose transport.