Dipartimento di Scienze Biochimiche A. Rossi Fanelli, Sapienza Università di Roma, Italy.
Int J Biol Macromol. 2010 Jan 1;46(1):37-46. doi: 10.1016/j.ijbiomac.2009.09.009. Epub 2009 Oct 6.
Structural adaptation of serine hydroxymethyltransferase (SHMT), a pyridoxal-5'-phosphate dependent enzyme that catalyzes the reversible conversion of l-serine and tetrahydropteroylglutamate to glycine and 5,10-methylene-tetrahydropteroylglutamate, synthesized by microorganisms adapted to low temperatures has been analyzed using a comparative approach. The variations of amino acid properties and frequencies among three temperature populations (psychrophilic, mesophilic, hyper- and thermophilic) of SHMT sequences have been tested. SHMTs display a general increase of polarity specially in the core, a more negatively charged surface, and enhanced flexibility. Subunit interface is more hydrophilic and less compact. Electrostatic potential of the tetrahydrofolate binding site has been compared. The enzyme from Psychromonas ingrahamii, the organism with the lowest adaptation temperatures, displayed the most positive potential. In general, the property variations show a coherent opposite trend in the hyperthermophilic population: in particular, increase of hydrophobicity, packing and decrease of flexibility was observed.
已采用比较方法分析了适应低温的微生物合成的丝氨酸羟甲基转移酶（SHMT）的结构适应性，该酶是一种依赖于吡哆醛-5'-磷酸的酶，可催化 l-丝氨酸和四氢蝶酰谷氨酸向甘氨酸和 5,10-亚甲基四氢蝶酰谷氨酸的可逆转化。已测试了 SHMT 序列的三个温度群体（嗜冷、中温和超嗜热）中氨基酸性质和频率的变化。SHMT 表现出极性的普遍增加，特别是在核心中，带负电荷的表面增强，柔韧性增强。亚基界面更亲水，更不紧凑。已比较了四氢叶酸结合位点的静电势。来自 Psychromonas ingrahamii 的酶（适应温度最低的生物体）显示出最正的电势。一般来说，超嗜热种群中的特性变化表现出一致的相反趋势：特别是，观察到疏水性、包装增加和柔韧性降低。
