These are Mr.Chou's enzyme problems: 1. The techniques of in vitro mutugeneses provide a powerful method for chemical modification of proteins or enzymes at will to examine the structure- function relationship. How to apply this approach to study the role of serine at the active site of trypsin? In the conventional chemical modification method, how to determine whether tyrosine residue is involved in the catalysis of cative site? What is the advantage or disvantage of this method as compared to site-specific mutagenesis? 2. For the thermodynamic study of tyrosine-tRNA synthetase, how do you determine the free energy of activation to the transition state(DG#) from the kinetic constants, e.g. Kcat and Km for the binding of Tyr and ATP to the enzyme. 4. What si the specific activity (Q) fo an enzyme? How to relate the specific activity to absolute enzyme purity P(mg of enzyme per mg of total protein) if the molecular weight(M) and the turnover number (Kcat, mole of product produced per min per mole of enzyme) of the enzyme are known. Write an expression for Q in terms of P, M and Kcat. 6. The concept of isozymes is derived from the study of lactate dehydrogenases (LDH). We know there are two types of subunits in LDH, H&M types. H subunits is predominant in aerobic tissue such as heart and M in anaerobic tissue as in skeletal muscle. For all oter tissues, LDH usually is present in mutiple molecular forms, how many forms can be detected if we know LDH is a tetramer of subunit mole. weight 37,000? An antiserum against M-type isozyme of one species but not with its own H-type enzymes. How to explain these discrepancies on the bias the structures of H and M subunits. --

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