Glucose-6-phosphate transport activity in liver microsomes exposed to stilbene disulfonate derivatives
Glucose-6-P (G6P) hydrolysis by hepatic microsomes (MS) is mediated by a coupled system composed of the G6P transporter (T1), the enzyme (E) and a phosphate transporter (T2). Zoccoli et al. concluded that T1 is a 54 kDa protein based on a linear correlation of labeling by /sup 3/H-4,4'diisothiocyano-1,2-diphenylethane-2,2'-disulfonate (/sup 3/H-H/sub 2/DIDS) and inhibition of system activity. The authors cannot support this conclusion: (1) in their hands the reaction of /sup 3/H-H/sub 2/DIDS with MS proteins is extremely nonspecific, and (2) the linear correlation must be between labeling and inhibition of T1 activity, because transport per se is not the absolute rate limiting step in hydrolysis by the system. Point 2 is readily demonstrated by examining the influence of the enzyme inhibitor, D-glucose, on the sensitivity of the system to inhibition by H/sub 2/DIDS. Studies of H/sub 2/DIDS inhibition of the system in MS from fasted and diabetic rats revealed that the observed inhibition constant for the system, K/sub i(S)/, is inversely proportional to the fraction of latent G6Pase activity (LF) seen before exposure to H/sub 2/DIDS, and K/sub i(S)/ x LF - K/sub i(T1)/, the inhibition constant for T1 activity. This relationship is derived from the equation 1/V/sub (S)/ - 1/V/sub (E)/ = 1/V/sub (T1)/, where V denotes the initial rates of S, E and T1, respectively. The latter equation can be used to calculate V/sub (T1)/ for any preparation of intact MS, and it predicts that labeling and inhibition of T1 will be linearly correlated with V/sub (T1)/ but not V/sub (S)/.
- Research Organization:
- Cornell Univ., Ithaca, NY
- OSTI ID:
- 7246643
- Report Number(s):
- CONF-8606151-; TRN: 86-039064
- Journal Information:
- Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States), Vol. 45:7; Conference: 76. annual meeting of the Federation of American Society for Experimental Biology, Washington, DC, USA, 8 Jun 1986
- Country of Publication:
- United States
- Language:
- English
Similar Records
Calcium transport in tonoplast and endoplasmic reticulum vesicles isolated from cultured carrot cells. [Daucus carota Danvers]
An investigation of the shedding of macromolecules from the Ehrlich mouse ascites tumor cell
Related Subjects
PHOSPHATES
MEMBRANE TRANSPORT
SULFONATES
BIOLOGICAL EFFECTS
GLUCOSE
HYDROLYSIS
LIVER
MICROSOMES
RATS
TRACER TECHNIQUES
TRITIUM COMPOUNDS
ALDEHYDES
ANIMALS
BODY
CARBOHYDRATES
CELL CONSTITUENTS
CHEMICAL REACTIONS
DECOMPOSITION
DIGESTIVE SYSTEM
GLANDS
HEXOSES
ISOTOPE APPLICATIONS
LABELLED COMPOUNDS
LYSIS
MAMMALS
MONOSACCHARIDES
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
ORGANOIDS
ORGANS
OXYGEN COMPOUNDS
PHOSPHORUS COMPOUNDS
RODENTS
SACCHARIDES
SOLVOLYSIS
VERTEBRATES
550201* - Biochemistry- Tracer Techniques