Effects Of Environmental Factors On Extracelluar Carbonic Anhydrase Activity Of Isochrysis Galbana

Carbonic anhydrase (EC 4.2.1.1), a ubiquitous mental enzyme that can catalyze the transformation reaction between HCO3- and CO₂,is one of enzymes whose catalytic velocity are confirmed to be the fastest. Many algae have caronic anhydrase.Some lie in intracelluare, others lie in the surface of cells.Moreover, carbonic anhydrase is a induced enzyme, whose activity depends on the around surroundings. Isochrysis galban is cultured in different condititon and assay its extracelluar carbonic anhydrase activity.The expression of extracelluar carbonic anhydrase can be effected by several environmental factors in Isochrysis galbana. In this paper it was mainly researched the effects of environmental factors on extracelluar carbonic anhydrase, such as CO₂, pH, HCO₃^-, N-sources, PO₄^3-, Zn²⁺. Then in order to research the interactive effects of environmental factors (NO3-, PO₄^3-, Zn²⁺) on extracelluar carbonic anhydrase in Isochrysis galbana, three environmental factors were selected to go on uniform-test. The results show: (1) Isochrysis galbana had the basic activities of extracelluar carbonic anhydrase, and with the growth of cell density, the activities of extracelluar carbonic anhydrase rose. The results showed that pH compensation point of Isochrysis galbana was 9.86, which suggested Isochrysis galbana can utilize HCO3-. (2) The effect of environmental factors on extracelluar carbonic anhydrase: The expression of extracelluar carbonic anhydrase can be inhibited by a higher CO₂ concentration, and the more higher CO₂ concentration, the more inhibitive. The extracelluar carbonic anhydrase activity is much higher at alkalinity pH than that of at acidity pH. The activity was apparently improved when pH rose from 6.5 to 9.0, and the highest ativity was induced at pH 8.5. The extracelluar carbonic anhydrase activity can be raised by affixioning HCO₃^-, which has the higest activity when the concentration of HCO3- is 2.0mmol/L. NO₃^-N 2.0mmol/L,PO₄^3--P 0.5mmol/L, Zn²⁺ 10μmol/L. (3)The results of uniform-test show:NaNO₃ (2.8mmol/L), NaH2PO4(0.2mmol/L), ZnSO₄ (6μmol/L).And other conditions:HCO₃^-(2.0mmol/L), pH(8.5),temperature (23士1℃), light intensity (4000lx).In this condition Isochrysis galbana had higher cell density and extracelluar carbonic anhydrase activity.