Expression of dipeptidyl peptidase III in normal lenses of rat of different ages

Abstract

Background It has been determined that dipeptidyl peptidase Ⅲ (DPPⅢ) plays an important role in the metabolism and modification of proteins and DPPⅢ of human has highly homologous to rat.Researches have shown that DPPⅢ is associated with the formation of cataract.However,few relevant studies have been reported.ObjectiveThe present study is to find out the relationship between the expression of DPPⅢ in rat lenses and age-related cataract.Methods Lenses were obtained from general Wistar rats of ages 3,6,9,or 12 weeks old (10 lenses each ) and homogenized with different concentrations of standard bovine serum.The proteins were resolved using SDS-PAGE gel electrophoresis.Peak concentration and total concentration of DPPⅢ protein in lenses from rats of different ages were detected by Western blot.Enzyme activity of DPPⅢ was determined by monitoring the amount of dipeptides removed from a special substrate (Arg-Arg-4mb NA) by measuring the absorbance with UV-2500PC at 525 nm.The relationship between the enzyme activity of DPPⅢ in lenses and age of rats was evaluated using regression analysis.Results DPPⅢ was detected at a molecular weight of 82000 Da.The peak concentration and total concentration of DPPⅢ in normal rat lenses increased with the growth of age.The total protease activity of DPPⅢ in the lenses of rats was correlated with the ages of the rats (r=0.99,P＜0.05).Conclusion DPPⅢ may be involved in the alteration of crystallin during the development of lenses,and it may play an important role in the formation and aggravation of age-related cataract. Key words: dipeptidyl peptidase Ⅲ; lens; age-related cataract; enzymes activity