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Glomerular filtration rate (GFR), the marker of chronic kidney disease can be analyzed by the concentration of cystatin C or creatinine and its clearance in human urine and serum samples. The determination of cystatin C alone as an indicator of GFR does not provide high accuracy, and is more expensive, thus measurement of creatinine has an important role in estimating GFR. We have made an attempt to quantify creatinine based on its pseudoenzyme activity of creatinine in the presence of copper. Creatinine in the presence of copper oxidizes paraphenylenediamine dihydrochloride (PPDD) which couples with dimethylamino benzoicacid (DMAB) giving green colored chromogenic product with maximum absorbance at 710 nm. Kinetic parameters relating this reaction were evaluated. Analytical curves of creatinine by fixed time and rate methods were linear at 8.8-530 μmol L(-1) and 0.221-2.65 mmol L(-1), respectively. Recovery of creatinine varied from 97.8 to 107.8%. Limit of detection and limit of quantification were 2.55 and 8.52 μmol L(-1) respectively whereas Sandell's sensitivity and molar absorption coefficient values were 0.0407 μg cm(-2) and 0.1427×10(4) L mol(-1) cm(-1) respectively. Precision studies showed that within day imprecision was 0.745-1.26% and day-to-day imprecision was 1.55-3.65%. The proposed method was applied to human urine and serum samples and results were validated in accordance with modified Jaffe's procedure. Wide linearity ranges with good recovery, less tolerance from excipients and application of the method to serum and urine samples are the claims which ascertain much advantage to this method.
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http://dx.doi.org/10.1016/j.saa.2012.02.104 | DOI Listing |
Structure
July 2025
Department of Biological Science, Florida State University, Tallahassee, FL 32306, USA; Institute of Molecular Biophysics, Florida State University, Tallahassee, FL 32306, USA. Electronic address:
GTPases regulate cellular processes through conformational changes triggered by guanine nucleotide binding. Recently, pseudoGTPases, the catalytically inactive counterparts of GTPases, have been identified across species from bacteria to human, although their functions and mechanisms remain unexplored. Here, we demonstrate that the N-terminal region of the assembly chaperone AAGAB is a class I pseudoGTPase using biochemistry and X-ray crystallography.
View Article and Find Full Text PDFInt J Biol Macromol
June 2025
State Key Laboratory of Microbial Technology, Institute of Microbial Technology, Shandong University, Qingdao 266237, China. Electronic address:
Enzymes, as vital biomacromolecules, have developed significant plasticity, enabling adaptation to diverse environments and catalysis of numerous biochemical reactions. However, enzyme evolution is constrained by mutational limitations, as amino acid substitutions often impair structure or function, hampering optimization endeavors. To address this, we integrated structural bioinformatics with site-directed mutagenesis to investigate the evolutionary trends of four GH11 family xylanases (XynA, XynB, XynD, and XynE) from Aspergillus niger An76.
View Article and Find Full Text PDFProteins
June 2025
Department of Chemistry and Biochemistry, James Madison University, Harrisonburg, Virginia, USA.
Starch accumulation in plants provides carbon for nighttime use, for regrowth after periods of dormancy, and for times of stress. Both ɑ- and β-amylases (AMYs and BAMs, respectively) catalyze starch hydrolysis, but their functional roles are unclear. Moreover, the presence of catalytically inactive amylases that show starch excess phenotypes when deleted presents questions on how starch degradation is regulated.
View Article and Find Full Text PDFbioRxiv
November 2024
Department of Biological Science, Florida State University, Tallahassee, FL 32306, USA.
PLoS One
February 2024
Université de Strasbourg, CNRS, Inserm, IGBMC UMR 7104- UMR-S 1258, F-67400 Illkirch, France.
Tubulin tyrosine ligase 12 (TTLL12) is a promising target for therapeutic intervention since it has been implicated in tumour progression, the innate immune response to viral infection, ciliogenesis and abnormal cell division. It is the most mysterious of a fourteen-member TTL/TTLL family, since, although it is the topmost conserved in evolution, it does not have predicted enzymatic activities. TTLL12 seems to act as a pseudo-enzyme that modulates various processes indirectly.
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