China
Africa
Explore chapters and articles related to this topic
Advantages of Enzymatic Peptide Synthesis
Published in Willi Kullmann, Enzymatic Peptide Synthesis, 1987
Both the enolization and the oxazolone-forming mechanism of Cα-Conversion are initiated by a base-catalyzed reversible withdrawal of the Cα-hydrogen, resulting in symmetric intermediates which can be unspecifically reconverted to l- and d-enantiomers (Figure 1). Similarly, the amino acid racemase mechanism also leads via Cα-hydrogen-abstraction to a symmetric intermediate, which is bound through a Schiffs base to pyridoxal phosphate,9 the co-factor of the racemase. Although the chemistry of α-carboxyl activation, via formation of active esters, is comparable in conventional and enzymic peptide synthesis, the relative three-dimensional structure of the binding-site of the proteases obviously enables catalysis to be stereospecific thus preventing the proteases from acting as racemases.
Urinary D-serine level as a predictive biomarker for deterioration of renal function in patients with atherosclerotic risk factors
Published in Biomarkers, 2019
Hidehiro Iwakawa, Shin Makabe, Tomokazu Ito, Tohru Yoshimura, Hiroyuki Watanabe
Urine samples were obtained in the early morning from patients who had fasted overnight. The samples were centrifuged at 10,000 × g for 5 min and stored at −20 °C until the analysis. The most widely used modality to measure D- and L-serine concentrations is high-performance liquid chromatography (HPLC) (Karakawa et al.2015, Xing et al.2016, Onozato et al.2017). However, HPLC is time consuming. In this study, urinary D- and L-serine concentrations were measured using an enzymatic assay, which is specific and simple, in combination with HPLC at the Department of Applied Molecular Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan (Ito et al.2007). Briefly, D-serine was assayed by determining the amount of pyruvate produced by D-serine dehydratase. Yeast D-serine dehydratase acts on both D- and L-serine. Therefore, D-serine dehydratase was applied to the determination of L-serine by coupling it with an amino acid racemase acting on L-serine. Urinary liver-type fatty acid-binding protein (L-FABP) was measured using an enzyme-linked immunosorbent assay kit from CMIC (Tokyo, Japan). The urinary N-acetyl-beta-D-glucosaminidase (NAG) level was determined using a colorimetric assay. The eGFR was calculated from serum creatinine using the modification of diet in renal disease equation with the Japanese coefficient (Matsuo et al.2009). Huang et al. (1998) reported that within-day urinary D- and L-serine values vary but for a given individual both are relatively constant when corrected by the urinary creatinine level. In a similar manner, urinary D- and L-serine were expressed as a ratio to the urinary creatinine concentration. Urinary L-FABP and albumin were also expressed as a ratio to the urinary creatinine concentration. Urinary NAG was expressed in U/L. The normal ranges of urinary L-FABP, albumin/creatinine ratio (UACR), and NAG are <8.4 μg/g creatinine,<30 mg/g creatinine, and <5.6 U/L, respectively.