Juicy Honey Peach Storage Temperature Optimization By Metabolic Network Flux Control Evaluation

In case that Juicy honey peach(JHP)is not only a respiration climacteric fruit,but also a sucrose accumulation type one,Choosing the proper storage temperature can effectively reduce the respiratory metabolic intensity and delay the postharvest ripening and senescence of fruit,while maintaining its quality,especially the fruit Sweetness and acidity.Sucrose is a key indicator of JHP quality,and lactic acid’s flux can quantitatively describe the strength of respiratory metabolism.In this research,JHPs were grouped and stored at different temperatures(0℃,5℃,10℃,15℃,20℃,25℃,30℃,35℃,40℃ and 45℃)for 24 hours,and then samples were fractionated from three parts of JHP(peel part,pulp part and near core part);Metabolic flux analysis(MFA)used to study the effect of JHP storage temperature on its sucrose accumulation and lactic acid flux,And Metabolic control analysis(MCA)was further use to correlate the flux variation of critical metabolic pathways(including sucrose synthesis pathway,lactate production pathway,etc.)with the activity variation of critical enzymes and the content variation of metabolites.The Elasticity coefficient(EC)and Flux control coefficient(FCC)are calculated and compared to analyze the key enzymes for sucrose.And the degree of control of the metabolic flux of the lactate production pathway.The obtained diagram of metabolic flux of sucrose and lactic acid showed that: 4℃were the optimal storage temperature for JHPs,at which the level of sucrose synthesis flux was the highest,and the flux variances of sucrose a mong selected three parts was lower: At the same time,the level of lactic acid synthesis flux was also the highest,and the flux variances of lactic acid flux among selected three parts was lower.Results obtained by Lin-log analysis(LLA)showed that: Sucrose phosphate synthase(SPS)has the strongest control effect on the flux of sucrose synthesis pathway(FCCSPS = 0.4982);Phosphoglucose isomerase(PGI),lactate dehydrogenation Enzymes(Lactate dehydrogenase,LDH)and Phosphofructokinase(PFK)have a strong control effect on the flux of the lactate metabolism pathway,and their flux control coefficients were FCCPGI = 0.1521,FCCLDH = 0.1476,and FCCPFK = 0.1146.Triose isomerase(Phospho-glucose isomerase,TPI),hexokinase(Hexokinase,HK)and 6-phosphate glucose dehydrogenase(6-phosphate glucose dehydrogenase,G6PDH)all have small fluxes for lactate metabolism Control effect,their control coefficients were FCCTPI = 0.0135,FCCHK = 0.0452 and FCCG6 PDH =-0.0302.Results obtained by principal component analysis(PCA)showed that: lactate dehydrogenase(LDH),phosphofructokinase(PFK),aldolase(ALD)and phosphate glucose isomerase(PGI)on the lactate metabolism pathway Flux has a strong control effect,and their control coefficients were CCPLDH = 0.1128,CCPPFK = 0.1076,CCPALD = 0.1021,and CCPTPI = 0.0988;6-phosphate glucose dehydrogenase(G6PDH)has the least control effect on lactic acid metabolic flux(CCPG6PDH = 0.0052).The two analysis methods in the lactic acid pathway have good consistency,and the correlation is as high as 0.905,which is significantly related at the 0.01 level.