Cloning and genes expression analyses of 2-acetyl-1-pyrroline biosynthesis-related enzymes in vegetable soybean

• Main Authors: Jian-Kai Chen, 陳建凱
• Other Authors: Mei-Li Wu
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/97934894949300315936

碩士 === 國立屏東科技大學 === 食品科學系 === 93 === 2-acetyl-1-pyrroline (2AP) has been reported as a potent flavor component of aromatic rice, taro, pandan ,and green soybean. During growing to vegetable soybean, 2AP levels in the young seeds increased with increasing maturity. The nitrogen source of pyrroline of 2AP structure was praline, but the acetyl-group has not been well-characterized. On the other hand, methylglyoxal, the putative precursor of 2AP may derive from dihydroxyacetone phosphate (DHAP) through triosephosphate isomerase catalysis. In this study, the key enzymes from vegetable soybean for 2AP biosynthesis, including, the subunit A (GapA), B (GapB) and C (GapC) of glyceraldehydes-3-phosphate dehydrogenase, triosephosphate isomerase (TIM) and ornithine-δ-aminotransferase (OAT) were cloned. These genes were overexpressed in Escherichia coli or Pichia pastoris. Specific activities of GapA, GapB, GapC, TIM and OAT of the recombination proteins purified by Ni2+ affinity column were determined as 9.8, 7.9, 27.4, 46.7 and 50.8 U/mg, respectively. Expression levels of these gene encoding key enzymes between aromatic and non-aromatic vegetable soybean was campared by RT PCR. No significant variation among OAT, P5CS and PDH genes was observed. However, higher TIM and lower GapC expression in aromatic vegetable soybean was found. Therefore, we hypothesized that TIM and GapC are closely related to the 2AP biosynthesis in aromatic vegetable soybean.