A new biocatalytic route to enantiopure N-carbamoyl amino acids by fast enzyme screening

The enantioselective enzymatic deamidation of (rac)-N-carbamoyl amino acid amides (Cbm-AA-NH₂) to enantiopure (L)-N-carbamoyl amino acids (Cbm-AA-OH) is described for the first time. Via fast screening methods of biocatalysts several proteases like Chirazyme P1, Chirazyme P2 and Subtilisin were identified, which give conversions of up to 47% and >98% ee. This conversion is most productive on aliphatic and primary amino acids.     

(S)‐Selective Kinetic Resolution and Chemoenzymatic Dynamic Kinetic Resolution of Secondary Alcohols

(S)‐Selective kinetic resolution was achieved through the use of a commercially available protease, which was activated with a combination of two different surfactants. The kinetic resolution (KR) process was optimized with respect to activation of the protease and to the acyl donor. The KR proved to be compatible with a range of functionalized sec‐alcohols, giving good to high enantiomeric ratio values (up to >200). The enzymatic resolution was combined with a ruthenium‐catalyzed racemization to give an (S)‐selective dynamic kinetic resolution (DKR) of sec‐alcohols. The DKR process works under very mild reaction conditions to give the corresponding esters in high yields and with excellent enantioselectivities.     

Simultaneous determination of D- and L-serine in rat brain microdialysis sample using a column-switching HPLC with fluorimetric detection

Both D- and L-serine in rat brain microdialysis sample were simultaneously determined by pre-column fluorescence derivatization with 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F), separation of the derivatives on ODS column, TSKgel ODS-80TsQA, followed by Pirkle type chiral columns, Sumichiral OA-2500 (S), which gave a sufficient enantiomeric separation of NBD-D-serine and NBD-L-serine, and fluorimetric detection at a wavelength of 540 nm with an excitation wavelength of 470 nm. The peaks of NBD-D-serine and NBD-L-serine in the rat brain microdialysis sample were clearly found, and the validation study showed satisfactory results; the precision and accuracy were within 5.14 and 109%, respectively. Using the proposed HPLC method, the time-course profile of D-serine concentration in rat prefrontal cortex following intraperitoneal administration of D-serine was investigated. As a consequence, D-serine appeared to be rapidly distributed in the brain, and then decreased gradually with time in the extracellular fluid of the rat prefrontal cortex. The proposed HPLC method will be useful for in vivo studies on D-serine, which acts as a coagonist for N-methyl-D-aspartate receptor, to the extracellular fluid of rat brain.     

丝氨酸-BrO^-~3-Mn^2^+-H2SO4体系振荡反应的研究

首次报道了间歇釜中以丝氨酸(Ser)-BrO^-~3-Mn^2^+-H2SO4为体系(简称Ser-BZ体系)的新型BZ类振荡反应,其特征如下：(1)虽然Ser不能发生溴代反应,但即使在无丙酮或惰性气体流时也能在间歇釜中观察到持续振荡;(2)振荡诱导期极短(～0),振荡次数较少(<11次);(3)振荡反应受到Cl^-,Br^-,丙烯腈等的抑制;但当加入足够量Ag^+使[Br^-]的振荡抑制后,仍可在Pt电极上观察到振荡现象。根据上述特征和反应产物分析,推测Ser-BZ振荡反应可能是自由基-控制模型,而非Br^--控制模型。加入适量丙酮可诱导连续振荡反应,归因于两种控制模型的共存。通过对Mn^3^+-Ser和BrO^-~3-Mn^2^+反应的动力学研究,并结合FKN机理,对Ser-BZ振荡反应机理进行了初步讨论。     

Thermal polycondensation synthesis of biomimetic serine-containing derivatives of polyaspartate: Potent inhibitors of calcium carbonate and phosphate crystallization

Biocompatable, degradable polymers that are powerful inhibitors of mineral formation were synthesized by automated solid phase and thermal polycondensation techniques. These polymers are analogues of natural proteins isolated from CaCO₃ biomineral and consist primarily of polyaspartic acid and serine or modified serine residues. Phosphorylation of the serine residues greatly enhanced the inhibitory activity of the polymers. Synthesis in the presence of orthophosphoric acid resulted in the decomposition and modification of serine. These modified residues when incorporated into the polyaspartic acid also enhanced inhibitory activity of the polymers. © 1994 John Wiley & Sons, Inc.     

Heat capacity of <Emphasis Type="Italic">D</Emphasis>- and <Emphasis Type="Italic">DL</Emphasis>-serine in a temperature range of 5.5 to 300 K

Heat capacity of D- and DL-serine was measured using adiabatic calorimetry in a temperature range of 5.5 to 300 K, and then thermodynamic functions were calculated. The difference in heat capacity (C _PD-C _PDL) between two species indicates a small anomaly in D-serine near 15 K and a systematic excess over DL for temperatures > 30 K. This is much larger, than a difference in thermodynamic functions measured so far for the polymorphs of organic molecular crystals. The excess is fitted well to Einstein contribution with characteristic temperature of 185 K which is equivalent to vibrational mode at 129 cm⁻¹.     

Development of enzyme technology and enzyme engineering in China

Enzymes have been utilized in China for thousands of years for the production of various foods and alcoholic beverages. Today China manufactures and uses enzymes for not only the traditional areas of application, but is expanding the use of enzymes for a variety of nonfood areas. This report describes the present state of the art of enzyme manufacture and application in China today.     

营养盐对假微型海链藻中鞘脂合成的影响

丝氨酸棕榈酰转移酶(Serine Palmitoyltransferase, SPT)是鞘脂合成途径中的关键酶, 其表达水平的高低影响生物体内鞘脂的含量. 该实验利用荧光定量PCR和液相色谱―质谱技术分析了营养盐对假微型海链藻中SPT表达及鞘脂合成的影响. 结果表明: SPT在微藻细胞中的表达水平直接影响其鞘脂的合成, 且P饥饿促进SPT的表达和细胞内神经酰胺的合成, 进而影响假微型海链藻的生长; 而N饥饿抑制SPT的表达和细胞内神经酰胺的合成及假微型海链藻的生长.