Postnatal ontogeny of kinetics of porcine jejunal brush border membrane-bound alkaline phosphatase, aminopeptidase N and sucrase activities

Our objectives were to determine postnatal changes in the maximal enzyme activity (V-max) and enzyme affinity (K-m) of jejunal mucosal membrane-bound alkaline phosphatase, aminopeptidase N and sucrase using a porcine model which may more closely resemble the human intestine. Jejunal brush border membrane was prepared by Mg2+-precipitation and differential centrifugation from pigs of suckling (8 days). weaning (28 days), post-weaning (35 days) and adult (70 days) stages. p-Nitrophenyl phosphate (0-8 mM), L-alanine-p-nitroanilide hydrochloride (0-28 mM) and sucrose (0100 mM) were used in alkaline phosphatase, aminopeptidase N and sucrase kinetic measurements. V-max of alkaline phosphatase was the lowest in the adult (4.27 mumol-mg(-1) protein-min(-1)), intermediate in the suckling (9.75 mumol(.)mg(-1) protein(.)min(-1)) and the highest in the weaning and post-weaning stage (12.83 and 10.40 mumol(.)mg(-1) protein(.)min(-1)). K of alkaline phosphatase was high in the suckling and weaning stages (5.14 and 9.93 mM) and low in the adult (0.66 mM). V-max of aminopeptidase N was low in the suckling (7.04 mumol(.)mg protein(-1)-min(-1)) and high in the post-weaning stage (13.36 mumol(.)mg(-1)protein(.)min(-1)). K of aminopeptidase N was the highest in the two weaning stages (2.96 and 3.39 mW intermediate in the adult (2.33 mM) and the lowest in the suckling stage (1.66 mm). V-max of sucrase increased from the suckling to the adult (0.48-1.30 mumol(.)mg(-1)protein-min(-1)). K of sucrase ranged from 11.19 to 16.57 mM. There are dramatic postnatal developmental changes in both the maximal enzyme activity and enzyme affinity of jejunal brush border membrane-bound alkaline phosphatase, aminopeptidase N and sucrase in the pig. (C) 2002 Elsevier Science Inc. All rights reserved.