Laber B, Gomis-Rüth F X, Romão M J, Huber R
Max-Planck-Institute für Biochemie, Martinsried, Federal Republic of Germany.
Biochem J. 1992 Dec 1;288 ( Pt 2)(Pt 2):691-5. doi: 10.1042/bj2880691.
Escherichia coli dihydrodipicolinate synthase (DHDPS) (EC 4.2.1.52), the first enzyme unique to lysine biosynthesis, catalyses the condensation of pyruvate and aspartate beta-semialdehyde (ASA) by a ping-pong mechanism. Pyruvate binds first to the enzyme, forming a Schiff base with the epsilon-amino group of Lys-161, followed by binding of ASA. Km values of 0.57 and 0.55 mM were determined for pyruvate and DL-ASA respectively. 3-Bromopyruvate inhibits DHDPS with a Ki of 1.6 mM. DHDPS is 50% inhibited by 1.0 mM-L-lysine, 1.2 mM-sodium dipicolinate or 4.6 mM-S-2-aminoethyl-L-cysteine. Crystals of DHDPS diffracting to beyond a resolution of 0.24 nm (2.4 A) were obtained under several experimental conditions. Diffraction patterns were compatible with trigonal space groups P3(1)21 or P3(2)21, with unit-cell parameters a = b = 12.26 nm and c = 11.19 nm. The density of the crystals indicates the presence of a dimer of DHDPS subunits per asymmetric unit.
大肠杆菌二氢二吡啶二羧酸合酶（DHDPS）（EC 4.2.1.52）是赖氨酸生物合成中第一种独特的酶，通过乒乓机制催化丙酮酸和天冬氨酸β-半醛（ASA）的缩合反应。丙酮酸首先与该酶结合，与赖氨酸-161的ε-氨基形成席夫碱，随后ASA结合。丙酮酸和DL-ASA的Km值分别测定为0.57和0.55 mM。3-溴丙酮酸以1.6 mM的Ki抑制DHDPS。1.0 mM-L-赖氨酸、1.2 mM-二吡啶甲酸钠或4.6 mM-S-2-氨基乙基-L-半胱氨酸可使DHDPS受到50%的抑制。在几种实验条件下获得了衍射分辨率超过0.24 nm（2.4 Å）的DHDPS晶体。衍射图谱与三方空间群P3(1)21或P3(2)21相符，晶胞参数a = b = 12.26 nm，c = 11.19 nm。晶体密度表明每个不对称单元存在DHDPS亚基二聚体。
