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Abstract

1.1. UDPG-glycogen transglycosylase has been demonstrated in the major tissues of a crab (Cancer magister) and in the muscles of crabs (C. magister, Hemigrapsus nudus), a crayfish (Astacus cambarus), molluskus (Mytilus californianus Tegula funebralis), fishes (Pomoxis annularis, Salmo gairdneri, Aequidens portalegrensis) and amphibians (Rana pipiens, Bufo marinus).2.2. The crab muscle enzyme requires glucose-6-phosphate (glc-6-p) and has a pH optimum at 8·3. It is unstable in crude preparations, but is stabilized by addition of fluoride and glc-6-p.3.3. The enzyme activity is not associated with any specific sedimentable fraction in homogenates.4.4. Mixtures of homogenates of muscle with homogenates of hepatopancreas or eyestalk have an enzyme activity lower than predicted from the activities of homogenates assayed separately. The inhibitory effect of hepatopancreas homogenates is attributed to presence of hydrolytic enzymes, but the inhibitory effect of eyestalk extracts is attributed to a specific inhibitory factor.5.5. The inhibitory factor in eyestalk extracts is non-dialyzable; it is partly but not wholly destroyed by boiling, or treatment with 95 per cent alcohol or 1 N HNl in the cold. The factor is not soluble in ether.6.6. The inhibitory effect of eyestalk extracts varies with the stage of the donor in the intermolt cycle.7.7. Eyestalk extracts of crabs inhibit transglucosylase activity in muscle extracts from crabs, crayfis, mollusks and vertebrates.8.8. The possible relation of the inhibitory factor to the diabetogenic hormone of crustaceans, and to the control of carbohydrate metabolism, is discussed.