Hopkins Marine Station Student Paper

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Title: Comparison of thermal stability of MDH from algae (Ulva and Enteromorpha) found at different intertidal heights
Student Author(s): Marin-Spiotta, Erika
Faculty Advisor(s): Somero, George N.
Pages: 14
Location: Final Papers Biology 175H
Date: June 1996
Abstract: Animals from different latitudes and intertidal heights show differences in thermal stability of the enzyme malate dehydrogenase (MDH) suggesting that protein thermal stability may be important in establishing species distributions (Dahlhoff and Somero, 1993). I examined whether algae from different tidal zones exhibit similar variation in protein thermostability. Algae that are exposed to air and direct sunlight during the tidal cycle can experience temperatures of up to 37 C. The two algal species studied were the low intertidal species Ulva expansa and the high intertidal Enteromorpha spp., which are submerged only under the highest tides. Individuals from Ulva and Enteromorpha (Division Chlorophyta, Order Ulotrichiales, Family Ulvacea) were collected from the Monterey Harbor and from the Hopkins Marine Life Refuge beach in central California, respectively. Heat denaturations of MDH were performed at 45 C on algal homogenates of each species. In all four trials, the residual activity of Enteromorpha MDH was greater than that of Ulva MDH. These differences were statistically significant at 20 and 40 min (unpaired t-test, P=0.0026 and 0.0228, respectively), though the difference between overall rates of activity loss was not statistically significant. Further experimental approaches to studying thermostability enzymes in algae are proposed.