(full paper is archived in the Miller Library)
Title: The effect of acclimation to intertidal and subtidal conditions on the thermal stability of supernatant lactate dehydrogenase from two species of Porcelain crab (genus Petrolithes)
Student Author(s): Harrison, Rebekah J.
Faculty Advisor(s): Somero, George
Location: Final Papers Biology 175H
Date: June 1997
Abstract: In Monterey Bay, Porcelain crabs inhabit discrete vertical zones: Petrolithes cinctipes is found intertidally and P. manimaculis is found subtidally. Differences in maximal temperature and emersion time for each species are associated with their individual vertical zonation. The thermal stability of lactate dehydrogenase (LDH) in a homogenate supernatant from P. cinctipes is greater than that from P. manimaculis. Purification of LDH removes this difference, causing the thermal stability of purified LDH from P. cinctipes to decrease to that of P. manimaculis. Thus some extrinsic factor may influence the proteins' thermal stability. To determine whether the enzyme thermal stability could be altered, I acclimated crabs to various conditions of temperature and emersion. Temperature rose between 8-15 degrees C above ambient seawater temperature during the 5.5 hour emersion time in one treatment, but did not change in the constantly immersed treatment. High levels of mortality were only observed for P. manimaculis in the emersion treatment. Thermal stabilities of LDH in homogenate supernatants did not change over a 36 day acclimation period. Differences in LDH thermal stability between species persisted. These data suggest that the mechanism causing the difference in stability between supernatant and purified enzyme is a highly regulated and conserved trait which was not affected by conditions of the experiment.