PATHWAYS OF CARBOHYDRATE METABOLISM IN LOBSTER HEPATOPANCREAS

Abstract

Oxygen uptake by homogenates of lobster hepatopancreas was stimulated by the addition of Embden–Meyerhof, pentose cycle, and citric acid cycle intermediates as well as xylose. Acetate-1-C¹⁴oxidation was blocked by fluoracetate and glucose-1-C¹⁴oxidation fell by 80% with iodoacetate treatment. TPN and DPN increased glucose-1-C¹⁴oxidation by 140% and 20% and acetate-1-C¹⁴oxidation by 50% and 100% respectively. Large amounts of C¹⁴enter polysaccharide following treatment with glucose-1-C¹⁴or acetate-1-C¹⁴but very little enters after treatment with the same amount of gluconate-1-C¹⁴. Gluconate and xylose oxidation occurs in mitochondria-free preparations. In short-term tests with acetate-1-C¹⁴as substrate, most of the label in glycogen is on carbons 3 and 4 and the amount in the other positions can be explained on the basis of a 5–10% participation of the pentose cycle.