D-甘露庚酮糖, D-Mannoheptulose

D-Glucose is phosphorylated by glucokinase and three tissue-specific hexokinases to produce glucose-6-phosphate in humans. D-Mannoheptulose is a heptose that inhibits glucokinases and hexokinases from diverse organisms through competition with D-glucose (Ki = 0.25 mM). It blocks glucose oxidation and glucose-mediated insulin release from pancreatic islet cells. D-Mannoheptulose prevents the conversion of glucose to glucose-6-phosphate that can mediate the activation of the carbohydrate response element binding protein. By blocking glucose phosphorylation, D-mannoheptulose causes transient hyperglycemia in dogs when given at 1 g/kg but not at 8 mg/kg, although postprandial energy expenditure is increased at the lower dose.

Title: D-manno-Heptulose

CAS Registry Number: 3615-44-9

Additional Names: D-manno-Ketoheptose

Molecular Formula: C7H14O7

Molecular Weight: 210.18

Percent Composition: C 40.00%, H 6.71%, O 53.29%

Literature References: Isoln from the wet pulp of the fruit of the avocado tree, Persea gratissima Gaertn. f. (P. americana Mill.), Lauraceae: LaForge, J. Biol. Chem. 28, 511 (1917); Montgomery, Hudson, J. Am. Chem. Soc. 61, 1654 (1939); Richtmyer in Methods in Carbohydrate Chemistry R. L. Whistler et al., Eds. vol. 1, 173 (1962).

Properties: Large, transparent prisms from methanol, mp 151-152°. [a]D20 +29° (c = 2 in H2O). Sol in water. Usually accompanied by perseitol. Although perseitol is much more insol in water and methanol than D-manno-heptulose, clean separation of the two substances is not always easy and may require patient fractional crystn.

Melting point: mp 151-152°

Optical Rotation: [a]D20 +29° (c = 2 in H2O)