Purification and Characterization of Glucose-6-Phosphate Dehydrogenase from Rat Small Intestine

Abstract

Glucose-6-phosphate dehydrogenase (G6PD) was purified from rat small intestine with 19.2% yield and had a specific activity of 53.8 units per miligram protein. The pH optimum was determined to be 8.1. The purified rat small intestinal G6PD gave one activity, one protein band on native PAGE. The observation of one band on SDS/PAGE with an Mr of 48 kDa and a specific activity lower than expected may suggest the proteolytically affected enzyme or different form of G6PD in the rat small intestine. The activation energy, activation enthalpy, Q10, and optimum temperature from Arrhenius plot for the rat small intestinal G6PD were found to be 8.52 kcal/mol, 7.90 kcal/mol, 1.59, and 38 degrees C, respectively. The Km values for G6P and NADP+ were 70.1 +/- 20.8 and 23.2 +/- 7.6 microM, respectively. Double-reciprocal plots of 1/Vm versus 1/G6P (at constant [NADP+]) and of 1/Vm versus 1/NADP+ at constant [G6P]) intersected at the same point on the 1/Vm axis to give Vm = 53.8 U/mg protein.

Kinetic mechanism and some properties of glucose-6-phosphate dehydrogenase from sheep brain cortex

“…The effect of temperature on an enzyme catalyzed reaction is frequently expressed in terms of a temperature coefficient, Q 10 [13]. The activation enthalpy of G6PD from sheep brain cortex by the formula in [13] was calculated as 6.026 kcal/mole and these data are consistent with previously calculated data from other sources by other studies [19,20]. The optimum pH of the sheep brain cortex was also examined and was determined as pH 8.…”

Purification and Characterization of Polyphenol Oxidase from Hemşin Apple (Malus communisL.)

“…The logarithm of activity at each temperature (log k) was calculated; the temperature values were converted to kelvin and expressed as 1/T × 1000 -1 in a graph. [33] The slope of the Arrhenius was obtained using this graph. The E a value was obtained using this slope, as given below: The enthalpy (ΔH) was calculated according to the following formula: [34][35][36] ΔH ¼ E a À RxT…”

Purification and Characterization of Glucose-6-Phosphate Dehydrogenase from Pigeon Pea (Cajanus cajan) Seeds

“…NADPH produced is necessary for the reductive biosynthesis of fatty acids, isoprenoids and aromatic amino acids in the dark, for nitrogen assimilation in heterotrophic tissues and acts as cofactor for other antioxidative enzymes like glutathione reductase [6]- [12]. The NADPH and pentose phosphates produced also serves as the route of entry of 3 -5 carbon sugars to the glycolytic pathway [13].…”

“…The enzyme is widely distributed and has been isolated from microorganisms, plants and various mammalian tissues [13]- [18]. The first isolation of the enzyme was carried out from human erythrocytes by Yoshida and Huang [19].…”