Functionality Study Of Dawson Type Phosphomolybdic As Tyrosinase Inhibitors

Tyrosinase?EC 1.14.18.1?is a complex and copperish oxidoreductase with much multifunction,which has dual catalytic activity.Tyrosinase is closely related to the biosynthesis of melanin.Excess expression of tyrosinase can easily cause enzymatic browning of food,affect the appearance and quality of fruits and vegetables,and even result in huge economic loss.Therefore,the development for safe and effective tyrosinase inhibitor is crucial in the field of food preservation.Polyoxometalates?POMs?have special functional properties,which are widely applied in many fields.Previous studies in our laboratory have demonstrated that POMs have good application in enzyme inhibitors,bacteriostasis,the melanin biosynthesis and the enzymatic browning in fruits and vegetables.In this paper,the inhibitory effects of the nine kinds of Dawson type phosphomolybdate on tyrosinase were studied.By the further research on the penaeus vanname and fresh-cut apples,this paper explored its application prospect of preservation in aquatic products,fruits and vegetables.The main content of this paper are introduced as follows:?1?Five kinds of Dawson type phosphomolybdate(P₂Mo₁₇V,P₂Mo₁₆V₂ P₂Mo₁₅V₃,P₂Mo₁₄V₄ and P₂Mo₁₃V₅)were synthesized and characterized.The inhibitory effects of these compounds on the diphenolase activity of tyrosinase were researched by enzyme kinetics.The results showed that P₂Mo₁₇V,P₂Mo₁₆V₂ and P₂Mo₁₅V₃ could significantly inhibit tyrosinase activity,and these three compounds were reversible and competitive inhibition.However,0-1.0mmol/L P₂Mo₁₄V₄ had no obvious effects on tyrosinase,while P₂Mo₁₃V₅ could activate tyrosinase.?2?Four kinds of Dawson type phosphomolybdate(P₂Mo₁₈,P₂Mo₁₇Mn,P₂Mo₁₇Co and P₂Mo₁₇Ni)were synthesized and characterized.The inhibitory effects of these compounds on the diphenolase activity of tyrosinase were researched by enzyme kinetics.The results showed that P₂Mo₁₈,P₂Mo₁₇Mn,P₂Mo₁₇Co and P₂Mo₁₇Ni could effectively inhibit tyrosinase,and these compounds were reversible and competitive inhibition.The inhibitory effects of P₂Mo₁₇Mn,P₂Mo₁₇Co and P₂Mo₁₇Ni on tyrosinase were stronger to P₂Mo₁₈.Moreover,P₂Mo₁₇Mn,P₂Mo₁₇Co and P₂Mo₁₇Ni had different inhibitory effects,which might related to ionic radius of the transition metal.As the ionic radius was larger,the inhibition ability was stronger.?3?The application of P₂Mo₁₇Mn on the preservation of penaeus vanname were studied.The results showed that P₂Mo₁₇Mn could effectively inhibit the growth of microorganism in penaeus vanname as well as the increase of pH value and TVB-N content.By the menas of slowing down the decline of sensory quality and the change of the color L*,P₂Mo₁₇Mn could reduce the browning process and delay the deterioration of the penaeus vanname during storage at 4°C.?4?The effects of P₂Mo₁₇Mn on the preservation of fresh-cut apples were studied.The results showed that during storage at 4°C,P₂Mo₁₇Mn could effectively decrease moisture loss of fresh-cut apples and slow down the increase of the malonaldehyde content.During the process the activity of PPO was inhibited while the activity of POD was decreased.Then the application of P₂Mo₁₇Mn on the preservation of fresh-cut apples could reduce the decrease of sensory quality,keep good colour and lustre,reduce the browning process,improve the sensory quality,and prolong the shelf life of fresh-cut apple.