Leydier C, Clottes E, Couthon F, Marcillat O, Vial C
Biomembranes et Enzymes Associés, UPRESA 5013 Centre National de la Recherche Scientifique-Université Lyon I., Villeurbanne, France.
Biochem Mol Biol Int. 1997 Apr;41(4):777-84. doi: 10.1080/15216549700201811.
Second-derivative spectroscopy was used to determine the percentage of tyrosine residues that are exposed to solvent in rabbit MM-creatine kinase. Six residues, among the ten present per monomer, are solvent-exposed. The presence of creatine in the incubation medium does not modify this value. However, this number is decreased by one when the enzyme is incubated with saturating concentrations of MgADP. A dissociation constant for MgADP can be estimated and the obtained value (0.085 mM) is comparable to the Km for this substrate. Thus, a tyrosine residue is located near the MgADP binding site or is masked during protein conformational change induced by adenyl nucleotide binding.
利用二阶导数光谱法测定了兔肌酸激酶-MM中暴露于溶剂中的酪氨酸残基的百分比。每个单体中存在的10个酪氨酸残基中有6个暴露于溶剂中。孵育介质中肌酸的存在不会改变这个值。然而，当酶与饱和浓度的MgADP孵育时，这个数字会减少1个。可以估算出MgADP的解离常数，得到的值（0.085 mM）与该底物的Km值相当。因此，一个酪氨酸残基位于MgADP结合位点附近，或者在由腺苷核苷酸结合诱导的蛋白质构象变化过程中被掩盖。
