Meeting Abstract

1.5  Monday, Jan. 4  Species differences in the effects of exercise on the stability of the glycolytic enzyme LDH in porcelain crabs MEDINA-RUILOBA, Haydee; STILLMAN, Jonathon H.*; San Francisco State University; San Francisco State University stillmaj@sfsu.edu

Glycolytic activity in anaerobic tissues is maintained by the redox enzyme lactate dehydrogenase (LDH). In addition to generation of ATP, LDH activity allows glycolysis to continue during physiological hypoxia by the recycling of NAD⁺ and production of lactic acid. Because enzymatic proteins are only marginally stable, acidification can destabilize enzymes and reduce their functionality. LDH stability in 22 species of porcelain crabs varies by over several orders of magnitude, and is due to both intrinsic differences in the LDH molecule and, in species with high-stability LDHs, LDH-specific extrinsic protein stabilizers. We hypothesize physiological hypoxia induces the protein stabilizers. Crabs were exercised to exhaustion on three consecutive days or held as controls. Two species of porcelain crab were studied, one with (Petrolisthes donario) and one without (Petrolisthes cinctipes) extrinsic protein stabilizers. Aliquots of claw muscle homogenate supernatant were heated at 70°C for intervals between 0 and 60min. Residual LDH enzymatic activity assessed spectrophotometrically and time to 50% activity loss (half-life) calculated. In P. donario, LDH stability was significantly increased by exercise; mean half-life ranged from 100min in control to 2000min in exercised specimens. In contrast in P. cinctipes LDH stability was not significantly affected by exercise; mean half-life was 48min in control and 67min in exercised specimens. Work is presently underway to determine specific protein-interactions affected by exercise using co-immunoprecipitation as well as gene expression responses following exercise using cDNA microarrays in the same specimens from which LDH stability was assessed. Supported by NIH SCORE grant S06 GM52588 to JHS.