TYROSINASE - KINETIC-ANALYSIS OF THE TRANSIENT PHASE AND THE STEADY-STATE

被引:104
作者
ROS, JR
RODRIGUEZLOPEZ, JN
GARCIACANOVAS, F
机构
[1] UNIV MURCIA,FAC BIOL,DEPT BIOQUIM & BIOL MOLEC,E-30100 ESPINARDO,SPAIN
[2] UNIV CASTILLA LA MANCHA,ESCUELA UNIV POLITECN,DEPT QUIM FIS,ALBACETE,SPAIN
来源
BIOCHIMICA ET BIOPHYSICA ACTA-PROTEIN STRUCTURE AND MOLECULAR ENZYMOLOGY | 1994年 / 1204卷 / 01期
关键词
TYROSINASE; MELANIN BIOSYNTHESIS; MELANOGENESIS; ENZYME KINETICS; REACTION MECHANISM; METABOLIC PATHWAY;
D O I
10.1016/0167-4838(94)90029-9
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
The transient phase of tyrosinase activity acting on monophenols has been investigated. Although an analytical solution for the lag period (tau) cannot be obtained, its dependence on reagent concentration and pH is studied. It is established that decreases as the quantity of enzyme increases, although it increases when monophenol or pH are increased. The computer simulation shows those rate constants whose variations affect the transient phase most significantly. In addition, the steady state of the pathway is studied using tyrosinases from several sources such as mushroom, frog epidermis and grape. The kinetic analysis, which is based on not imposing restrictions on the values of the rate constants involved in the mechanism, allows us to obtain analytical expressions for both monophenolase and diphenolase activities and explains the experimental results obtained with the different enzymes. The values determined for the kinetic parameter, R, point to the monophenol hydroxylation step as being the limiting step of the turnover, while the values obtained for n suggest the absence of fast equilibrium in the oxidation of diphenol by E(met).
引用
收藏
页码:33 / 42
页数:10
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