D- and L-β-Hydroxybutyrate Dehydrogenases and the Evolution of Ketone Body Metabolism in Gastropod Molluscs

Autor: J. S. Ballantyne, J. McLeod, A. E. Bourns, E. L. Ooi, J. A. Stuart
Rok vydání: 1998
Předmět:
Zdroj: The Biological Bulletin. 195:12-16
ISSN: 1939-8697
0006-3185
DOI: 10.2307/1542770
Popis: In vertebrate animals, ketone bodies, synthesized primarily from stored lipid, are important metabolic substrates (1). During starvation, ketone bodies, acetoacetate (Acac) and {beta}-hydroxybutyrate (BHB), are oxidized by some extrahepatic tissues at high rates, and thus perform the important function of sparing limited glycogen stores (1, 2). The enzyme {beta}-hydroxybutyrate dehydrogenase (BHBDH), which catalyzes the interconversion of the ketone bodies, is found in all mammals and most vertebrates, but is absent in most invertebrates (1, 3), including marine molluscs (4). The highest measured BHBDH activities in the animal kingdom, however, are found in the hearts of terrestrial gastropod molluscs (5, 6). We have recently demonstrated that, in tissues of the terrestrial gastropod Cepaea nemoralis, two unique and previously unknown isoforms of BHBDH occur (5). The isoforms differ from the well-characterized mitochondrial membrane-bound D-BHBDH found in all other animals (7) in that they are cytosolic, and one isoform is specific for the L-enantiomer of BHB. Here we identify patterns in the evolution of these enzyme isoforms in the Gastropoda. BHBDH activities, stereospecificity and subcellular compartmentalization were measured in gastropod species representing four major groups with freshwater and terrestrial representation: Neritomorpha (primitive gilled gastropods), Architaenioglossa (more advanced gilled gastropods), Basommatophora (freshwater pulmonates), and Stylommatophora (terrestrial pulmonates). Mapping of these data onto a phylogeny of the Gastropoda (8) indicates that cytosolic D- and L-BHBDH have arisen a single time, in an ancestral stylommatophoran. All gastropods of the order Stylommatophora possess this unique organization of ketone body metabolism, which has not been found elsewhere in the animal kingdom.
Databáze: OpenAIRE
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