"Determination of cystathionine beta-synthase activity in human plasma by LC-MS/MS: potential use in diagnosis of CBS deficiency" . "Journal of Inherited Metabolic Disease" . . . "Determination of cystathionine beta-synthase activity in human plasma by LC-MS/MS: potential use in diagnosis of CBS deficiency"@en . "http://dx.doi.org/10.1007/s10545-010-9178-3" . . "RIV/00064165:_____/11:8960!RIV12-MZ0-00064165" . "Hn\u00EDzda, Ale\u0161" . "Krijt, Jakub" . . . "Moat, Stuart" . "Cystathionine Beta-synthase; Homocysteine; enzyme activity assay; mass spectrometry"@en . "Kopeck\u00E1, Jana" . . "Cystathionine beta-synthase (CBS) deficiency is usually confirmed by assaying the enzyme activity in cultured skin fibroblasts. We investigated whether CBS is present in human plasma and whether determination of its activity in plasma could be used for diagnostic purposes. We developed an assay to measure CBS activity in 20 mu L of plasma using a stable isotope substrate - 2,3,3-(2)H serine. The activity was determined by measurement of the product of enzyme reaction, 3,3-(2)H-cystathionine, using LC-MS/MS. The median enzyme activity in control plasma samples was 404 nmol/h/L (range 66-1,066; n = 57). In pyridoxine nonresponsive CBS deficient patients, the median plasma activity was 0 nmol/ho/L (range 0-9; n = 26), while in pyridoxine responsive patients the median activity was 16 nmol/hour/L (range 0-358; n = 28); this overlapped with the enzyme activity from control subject. The presence of CBS in human plasma was confirmed by an in silico search of the proteome database, and was further evidenced by the activation of CBS by S-adenosyl-L-methionine and pyridoxal 5'-phosphate, and by configuration of the detected reaction product, 3,3-(2)H-cystathionine, which was in agreement with the previously observed CBS reaction mechanism. We hypothesize that the CBS enzyme in plasma originates from liver cells, as the plasma CBS activities in patients with elevated liver aminotransferase activities were more than 30-fold increased. In this study, we have demonstrated that CBS is present in human plasma and that its catalytic activity is detectable by LC-MS/MS. CBS assay in human plasma brings new possibilities in the diagnosis of pyridoxine nonresponsive CBS deficiency." . "[BCED77A37AEA]" . "000286607000006" . . "RIV/00064165:_____/11:8960" . . . "Ko\u017Eich, Viktor" . . "NL - Nizozemsko" . "Cystathionine beta-synthase (CBS) deficiency is usually confirmed by assaying the enzyme activity in cultured skin fibroblasts. We investigated whether CBS is present in human plasma and whether determination of its activity in plasma could be used for diagnostic purposes. We developed an assay to measure CBS activity in 20 mu L of plasma using a stable isotope substrate - 2,3,3-(2)H serine. The activity was determined by measurement of the product of enzyme reaction, 3,3-(2)H-cystathionine, using LC-MS/MS. The median enzyme activity in control plasma samples was 404 nmol/h/L (range 66-1,066; n = 57). In pyridoxine nonresponsive CBS deficient patients, the median plasma activity was 0 nmol/ho/L (range 0-9; n = 26), while in pyridoxine responsive patients the median activity was 16 nmol/hour/L (range 0-358; n = 28); this overlapped with the enzyme activity from control subject. The presence of CBS in human plasma was confirmed by an in silico search of the proteome database, and was further evidenced by the activation of CBS by S-adenosyl-L-methionine and pyridoxal 5'-phosphate, and by configuration of the detected reaction product, 3,3-(2)H-cystathionine, which was in agreement with the previously observed CBS reaction mechanism. We hypothesize that the CBS enzyme in plasma originates from liver cells, as the plasma CBS activities in patients with elevated liver aminotransferase activities were more than 30-fold increased. In this study, we have demonstrated that CBS is present in human plasma and that its catalytic activity is detectable by LC-MS/MS. CBS assay in human plasma brings new possibilities in the diagnosis of pyridoxine nonresponsive CBS deficiency."@en . . "0141-8955" . . "Determination of cystathionine beta-synthase activity in human plasma by LC-MS/MS: potential use in diagnosis of CBS deficiency" . "Z(MSM0021620806), Z(MZ0VFN2005)" . "Kluijtmans, Leo AJ" . "2"^^ . . "1" . "34" . . "Determination of cystathionine beta-synthase activity in human plasma by LC-MS/MS: potential use in diagnosis of CBS deficiency"@en . . . . "193818" . "7"^^ . "7"^^ . . . "Mayne, Phillip" .