Hibino T, Meng Y L, Kawamitsu Y, Uehara N, Matsuda N, Tanaka Y, Ishikawa H, Baba S, Takabe T, Wada K, Ishii T, Takabe T
Faculty of Science & Technology, Meijo University, Nagoya, Aichi, Japan.
Plant Mol Biol. 2001 Feb;45(3):353-63. doi: 10.1023/a:1006497113323.
Glycinebetaine is an important osmoprotectant in bacteria, plants, and animals, but only little information is available on the synthesis of glycinebetaine in tree plants. Among four mangrove species, glycinebetaine could be detected only in Avicennia marina. Pinitol was the main osmoprotectant in the other three species. The level of glycinebetaine in A. marina increased under high salinity. Betaine-aldehyde dehydrogenase (BADH) was detected in all four species, but choline monooxygenase could not be detected. A cDNA library was constructed from the leaves of A. marina. Two kinds of BADH cDNAs were isolated, one homologous to the spinach chloroplast BADH, and the other with unique residues SKL at the end of C-terminus. The BADH transcription levels of the former were higher than those of the latter. The levels of the former BADH increased at high salinity whereas those of the latter were independent of salinity. BADHs were expressed in Escherichia coli and purified. Two kinds of A. marina BADHs exhibited similar kinetic and stability properties, but were significantly different from those of spinach BADH. A. marina BADHs efficiently catalyzed the oxidation of betainealdehyde, but not the oxidation of omega-aminoaldehydes and were more stable at high temperature than the spinach BADH.
甘氨酸甜菜碱是细菌、植物和动物中一种重要的渗透保护剂，但关于树木中甘氨酸甜菜碱合成的信息却很少。在四种红树林物种中，仅在白骨壤中能检测到甘氨酸甜菜碱。在其他三种物种中，松醇是主要的渗透保护剂。在高盐度条件下，白骨壤中甘氨酸甜菜碱的含量增加。在所有四种物种中均检测到了甜菜碱醛脱氢酶（BADH），但未检测到胆碱单加氧酶。从白骨壤的叶片构建了一个cDNA文库。分离出了两种BADH cDNA，一种与菠菜叶绿体BADH同源，另一种在C末端末尾具有独特的残基SKL。前者的BADH转录水平高于后者。在高盐度条件下，前者BADH的水平升高，而后者的水平与盐度无关。BADH在大肠杆菌中表达并进行了纯化。两种白骨壤BADH表现出相似的动力学和稳定性特性，但与菠菜BADH的特性明显不同。白骨壤BADH能高效催化甜菜碱醛的氧化，但不能催化ω-氨基醛的氧化，并且在高温下比菠菜BADH更稳定。
