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Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The in vitro vitamin K-dependent carboxylation of peptide- or protein-bound glutamate residues is generally studied in detergent-solubilized microsomes from rat or cow liver. Under the conditions usually employed, the efficiency of the carboxylation reaction is low (less than 1% of the carboxylatable residues is converted into gammacarboxyglutamate). Here we describe that this efficiency may be raised to 30% by carrying out the following adaptations: 1) carboxylase was purified about 100-fold from the solubilized microsomes, so that the enzyme was obtained in a highly concentrated form and could be added in excess: 2) the HCO-3 concentration in the reaction mixtures was raised to 50 mM and 3) a substrate was selected (decarboxylated osteocalcin from bovine bone) the Km of which had been shown to be low (10 microM) and it was added in rate-limiting amounts. Besides the fact that under these conditions the carboxylation reaction occurred with a higher efficiency than before, the adaptations also enabled us to express the carboxylation activity in terms of moles CO2 incorporated per mole of substrate.
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PMID:Vitamin K-dependent carboxylase: increased efficiency of the carboxylation reaction. 349

We have investigated the changes in biochemical markers and in pyridinium cross-links in bone in hypophosphatemic rats. Six-week-old female Wistar rats were divided into two groups (normal diet and a phosphate-deficient diet) and fed for 8 weeks. A low phosphate intake caused a significant difference in the concentrations of osteocalcin and alkaline phosphatase with advancing rachitis as well as an increase in bone resorption marker concentrations in urine. Femur biochemical analysis revealed a significant (p < 0.005) increase in deoxypyridinoline per mole collagen in the phosphate-deficient group which suggested that urinary excretions of pyridinium cross-links might reflect not only bone resorption but also increased pyridinium cross-links in bone matrix collagen. Our results demonstrate that a low phosphate intake causes an increase of pyridinium cross-link formation as well as a discrepancy between the circulation levels of alkaline phosphatase and osteocalcin with advancing rachitis. These alterations induced by low phosphate intake should be considered when interpreting the values of biochemical markers.
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PMID:Effects of low phosphate intake on bone and mineral metabolism in rats: evaluation by biochemical markers and pyridinium cross-link formation in bone. 962 81

When the properties of an analyte are known, the separation system can be designed to make the analyte of interest migrate at either a much faster or a much slower velocity compared to other molecules in the sample matrix. A simple and sensitive method to analyze the gamma-carboxyglutamic acid (Gla) content of protein, urine, and plasma was developed using capillary electrophoresis with laser-induced fluorescence detection (CE-LIF). The separation method is designed according to the specific properties of three amino acids of interest. The number of Gla residues from three vitamin K-dependent proteins were estimated by quantifying the amount of fluorescein thiocarbamyl derivative of Gla after alkaline hydrolysis and fluorescein isothiocyanate labeling. Human prothrombin, blood coagulation factor X, and bovine osteocalcin were calculated to have 10.0 +/- 0.7, 11.0 +/- 0.6, and 2.1 +/- 0.1 Gla residues per mole of protein, respectively, which agreed well with amino acid sequencing data. The analysis of free Gla content in urine and plasma was also demonstrated by this method. It was demonstrated that submicrograms of protein can be characterized by CE-LIF.
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PMID:Analysis of gamma-carboxyglutamic acid content of protein, urine, and plasma by capillary electrophoresis and laser-induced fluorescence. 1022 Oct 78

Lysyl oxidase (LOX)-mediated collagen crosslinking can regulate osteoblastic phenotype and enhance mechanical properties of tissues, both areas of interest in bone tissue engineering. The objective of this study is to investigate the effect of lysyl oxidase-like 2 (LOXL2) on osteogenic differentiation of mesenchymal stem cells (MSCs) cultured in perfusion bioreactors, enzymatic collagen crosslink formation in the extracellular matrix (ECM), and mechanical properties of engineered bone grafts. Exogenous LOXL2 to MSCs seeded in composite scaffolds under perfusion culture for up to 28 days is administered. Constructs treated with LOXL2 appear brown in color and possess greater DNA content and osteogenic potential measured by a twofold increase in bone sialoprotein gene expression. Collagen expression of LOXL2-treated scaffolds is lower than untreated controls. Functional outputs such as calcium deposition, osteocalcin expression, and compressive modulus are unaffected by LOXL2 supplementation. Excitingly, LOXL2-treated constructs contain 1.8- and 1.4-times more pyridinoline (PYD) crosslinks per mole of collagen and per wet weight, respectively, than untreated constructs. Despite these increases, compressive moduli of LOXL2-treated constructs are similar to untreated constructs over the 28-day culture duration. This is the first report of LOXL2 application to engineered, three-dimensional bony constructs. The results suggest a potentially new strategy for engineering osteogenic grafts with a mature ECM by modulating crosslink formation.
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PMID:Exogenous Lysyl Oxidase-Like 2 and Perfusion Culture Induce Collagen Crosslink Formation in Osteogenic Grafts. 3005 20