A Search Of The Network And Controlling Mechanism Of Sucrose And Lactate Metabolism Of Hami Melon During Storage

Cold storage of fruits and vegetables is essentially a respiring and metabolic networkflow and control process for which the further study of metabolic control rules are neededin order to improve the shelf-life of these living food products. This study used Hami melonas a test subject to study the respiratory metabolic network and flux control of fruits andvegetables during their storage. Hami melon was stored at different temperatures (0,5,10,15,20,25,30,35,40,45°C), in order to obtain the metabolic flux of the followingpathways: embden meyerhof pathway (EMP), pentose phosphate pathway (PPP), sucrosesynthesis pathway (SSP) and TCA cycle (TCA). The quantity and activities of Primaryenzymes (enzymatic expression variate) were measured during storage. In addition, we gotthe control coefficients of synthesis flux to sucrose and metabolic flux to lactate. Theresults showed that sucrose had a higher synthesis flux at the temperatures of5°C and45°C,and lactate had a higher metabolic flux at the temperature of5°C. The study on flux controlcoefficients indicated that sucrose phosphate synthase (SPS, FCC=0.424) produced a largerimpact on sucrose flux control in the sucrose synthesis pathway. Lactic dehydrogenase(LDH, FCC=0.143), triosephosphate isomerase (TPI, FCC=0.136) and pyruvate kinase (PK,FCC=0.136) had a large control effect on lactate flux, while glucose-6-phosphatedehydrogenase (G6PDH, FCC=-0.246) had a negative control function. These findings willenable future detailed investigation of metabolic mechanism of fruits.It is found that Glyceraldehyde3-phosphate dehydrogenase (GAPDH)，phosphoglycerate kinase (PGK)，acetone phosphate isomerase (TPI)，lactate dehydrogenase(LDH) and pyruvate kinase (PK) gene expression activity are significantly elevated at0℃.Gene expression activity of sucrose phosphate synthase is the highest at5℃. The geneexpressin activity of pyruvate dehydrogenase, malate dehydrogenase, phosphofructokinaseand other enzymes have a significant increase trend at45℃. The difference of temperaturescontrols the metabolic network by changing the genetic expression activity of all kinds ofenzymes in the metabolic network. By researching the metabolic flux control of respiratorymetabolism, central metabolism and sucrose and lactate metabolism, we provide a newtechnical method for the research on metabolic networks and flux control during theprocess of low temperature and modified atmosphere storage of fruits and vegetables. Itprovided a new method to ensure quality and flavor of fruits and vegetables under thepremise of maximizing its storage time.It is found that massages exchanged during different parts. The flux of sucrose have atrend of reducing firt and then increasing from outside to inside. Lactate flux is decreasing.However, temperature make a greater impact on the flux of lactate in pericarp. There is a highest fluxat the temperature of5℃and25℃. Two methods are used to analysis the Lactatemetabolism in Hami melon, principal component analysis and lin-log control analysis.Theresults showed that two methods are consistent. Principal component analysis can simplifythe process of metabolic process. This provides a new analytical method for the reserach ofmetabolic networks.