A comparative study of intestinal phlorizin hydrolase in various animal species.

-1. Phlorizin hydrolase activity has been determined in the intestinal homogenates of ten species. The activity decreased in the following order: frog, rabbit, squirrel, rat and monkey. The activity was either very low or could not be detected in chicken, pigeon, guinea-pig, goat and human. 2. The enzyme was optimally active in the pH range 5.0-5.7 in all the species investigated except in the squirrel for which the range was 4" 1-4"7. 3. The distribution of phlorizin hydrolase along the length of the intestine was almost similar in rat, rabbit and monkey and maximal activity is found in the midgut. 4. The developmental pattern for phlorizin hydrolase and lactase in rat intestine during growth was found to be markedly different. INTRODUCTION PHLORIZIN (phloretin-2'-fl-glucoside) is a naturally occurring plant glucoside distributed chiefly in root bark, bark, leaves and leaf buds of apple, cherry and other trees of the Rosaceae family. The role of this compound as a potent glucose transport inhibitor in mammalian intestine has been well documented (Crane, 1960; Alvarado & Crane, 1964). Recently, pMorizin was observed to undergo rapid hydrolysis in the brush borders of hamster intestine (Malathi & Crane, 1969). The enzyme catalyzing this hydrolysis was designated as phlorizin hydrolase and the available evidence suggested that it was different from lactase. Our preliminary studies revealed that the enzyme catalyzing the hydrolysis of phlorizin is present in a number of species such as primates, Rodentia, Lagomorpha (mammalian class), Neognathae (avian class) and Anura (amphibian class). The present paper deals with a comparative study of intestinal phlorizin hydrolase and lactase in different species of animals. A study has also been made of the development of lactase and phlorizin hydrolase in the rat during growth. MATERIALS AND METHODS Chemicals and enzymes The following chemicals and enzymes were purchased commercially as indicated: phlorizin and lactose from British Drug Houses Ltd., England and o-dianisidine, Tris