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Properties of Pteroylpolyglutamate Hydrolase in Pancreatic Juice of the Pig^1,2,3,

Food Science and Human Nutrition Department ^* College of Veterinary Medicine, University of Florida, Gainesville, FL 32611

The function of pteroylpolyglutamate hydrolase (PPH) of pancreatic secretion in the hydrolysis of dietary polyglutamyl folates (PteGlu_n) in humans is unclear. In this study, PPH was detected in pancreatic juice collected from pigs during both fasting and postprandial conditions. The secretion of PPH was markedly increased following feeding. Pancreatic PPH showed the following characteristics: 1) endo/random hydrolysis of gamma-glutamyl peptide bonds of Pte-Glu_n substrates, yielding folic acid as the terminal product; 2) maximum activity at pH 4.0–4.5 and maximum stability at pH 7.0; 3) stimulation of activity by Zn²⁺ and 2-mercaptoethanol; 4) K_m values for pteroyltriglutamate (PteGlu₃) of 28.7 µM at pH 4.0 and 9.1 µM at pH 5.0; 5) apparent molecular weight of 29,000; and 6) isoelectric point within the range of 8.5–9.0. On the basis of PPH activity, volume of the postprandial secretion and pH profile of enzyme activity, it is suggested that pancreatic PPH may act in vivo in folate digestion and absorption to initiate the deconjugation of dietary PteGlu_n prior to the action of jejunal brush border PPH.

KEY WORDS: • folate • pteroylpolyglutamate hydrolase • conjugase • pancreas • pig

¹ Presented in part at the 1988 meeting of the Federation of American Societies for Experimental Biology, New Orleans, LA [BHANDARI, S. D., GREGORY, J. F., RENUART, D. R. & MERRITT, A. M. (1989) Properties of pteroylpolyglutamate hydrolase (PPH) in pancreatic secretion of the pig. FASEB J. 3: A667 (abs. 2562)].

² Supported by Grant No. 86-CRCR-1-1938 from the Competitive Research Grants Office, U.S. Department of Agriculture. Daniel R. Renuart was supported as a predoctoral fellow by NIH Grant 5-T35-HL07489.

³ Florida Agricultural Experiment Station Journal Series No. R-00069.

⁴ To whom correspondence should be addressed.

Manuscript received 18 July 1989. Revision accepted 9 November 1989.

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