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Nutrient Metabolism

Intestinal Brush Border Membrane Catalyzes Hydrolysis of Pyridoxine-5'-ß-D-Glucoside and Exhibits Parallel Developmental Changes of Hydrolytic Activities Toward Pyridoxine-5'-ß-D-Glucoside and Lactose in Rats^{1 ,2 ,3}

Food Science and Human Nutrition Department, University of Florida, Gainesville, FL 32611

⁴To whom correspondence should be addressed. E-mail: jfgy{at}ufl.edu.

Pyridoxine-5'-ß-D-glucoside (PNG) is a major form of vitamin B-6 in plant foods that exhibits partial bioavailability as vitamin B-6 in humans. We previously identified an intestinal mucosal cytosolic PNG hydrolase that catalyzes the partial hydrolysis of PNG absorbed without prior deglycosylation. Recent observations that the brush border membrane also catalyzes PNG hydrolysis led to the hypothesis that PNG hydrolysis may be another function of the ß-glucosidase lactase-phlorizin hydrolase (LPH) and, thus, brush border PNG hydrolysis would undergo a developmental decline similar to that of lactose hydrolysis. In this study, the relationships among hydrolytic activities in small intestinal cytosolic and brush border fractions in rats (n = 9 per group) of various ages (1–2 d and 2, 4, 8, 12 and 24 wk) were examined. In vitro specific activities toward PNG and lactose were greater in brush border than cytosol, and these were greater in newborn rats than in all other age groups (P < 0.01). Brush border activities toward PNG and lactose and were closely correlated (r = 0.84; P < 0.0001). These findings suggest that the hydrolysis of PNG is catalyzed at least partially at the brush border and that the bioavailability of PNG may be influenced by the residual LPH activity in children and adults.

KEY WORDS: • vitamin B-6 • pyridoxine-5'-ß-D-glucoside • lactase-phlorizin hydrolase • rats • bioavailability

This article has been cited by other articles:

				A. D. Mackey, S. O. Lieu, C. Carman, and J. F. Gregory III Hydrolytic Activity toward Pyridoxine-5'-{beta}-D-Glucoside in Rat Intestinal Mucosa Is Not Increased by Vitamin B-6 Deficiency: Effect of Basal Diet Composition and Pyridoxine Intake J. Nutr., May 1, 2003; 133(5): 1362 - 1367. [Abstract] [Full Text] [PDF]