Study On Characterization Of Sugar Metabolism Related-enzymes In Grape Berries Before And After Veraison

Shang-24 of Chinese wild Vitis (V.quinguangularis, Reld) and Cabernet Sauvignon (V.vinifera L) were used as material in this study. By using the high performance liquid chromatograph (HPLC),enzymic kinetics, enzyme-linked immunosorbent assay (ELISA) and Western blotting, the changes of organic acid content, sugar content, sugar metabolism related-enzyme and the key enzyme of phenolic compounds biosynthesis in grape berries have been studied before and after veraison. These results will provide a theoretic base for the further studies on mechanism of sugar metabolism related-enzyme and improving quality of grape berry by using biotechnology.The results indicated that there were obvious changes in grape berries after veraison, organic acid declined, the malic acid decreased more rapidly than tartaric acid; the sugar content increased; the activity of amylase (α-amylase and β-amylase),soluble acid invertase (SAI),sucrose phosphate synthase (SPS),sucrose synthase (SS) and phenylalanine ammonia lyase (PAL) in the berries of Shang-24 and Cabernet Sauvignon also increased more remarkably comparing with those before veraison. Glucose and fructose were mainly accumulated in sugar accumulation of grape berries. Compared to Cabernet Sauvignon, Shang-24 sugar content was lower, but its activity of sugar accumulation related-enzyme was higher. This resulted from the high PAL activity, which made a number of sugar participation in biosynthesis of phenolic compounds in Shang-24 berries. Otherwise, there was a different activity between β-amylase and ASI in berries, which led to the difference of sugar metabolism. The Western blotting of β-amylase and acid invertase in berries of two species showed that β-amylase had the molecular mass of 58 kD; SAI had the molecular mass of 60 kD. Furthermore, we firstly found an isoenzyme of SAI with molecular mass of 105 kD in Shang-24 berries.The β-amylase activity in Shang-24 was higher than that in Cabernet Sauvignon, which was caused by two reasons. One was that the Km of β-amylase was lower in Sahng-24 berries, which led to the higher affinity of β-amylase with substance; the other was that the results of Western blotting and ELISA showed that gene expressing content of β-amylase in Shang-24 was much more than that in Cabernet Sauvignon.The SAI activity in Shang-24 berries was higher than that in Cabernet Sauvignon which was caused by two reasons. Firstly, the affinity of SAI with substance was higher in Shang-24 berries. Secondly, the results of ELISA showed the gene expressing content of SAI was higher in Shang-24 berries. Finally, the isoenzyme of SAI (150kD) in Shang-24 berries probably played an important role in sugar metabolism.