Determination of adenosine deaminase activity using high-pressure liquid chromatography

Determination of enzyme activity by high-performance liquid chromatography

The application of high-performance liquid chromatography (HPLC) in the study of enzymatic reactions is reviewed. The rationale for using HPLC is given and whether the components of the reaction mixture should be derivatized prior to or after HPLC. An alphabetical list of enzymes assayed by HPLC is given. Substrate and product are included as well the derivatization reagent, detection method and biological matrix. Specific examples of these assays in a complex biological matrix viz. faeces are given. Future prospects are the detection of new enzymes using synthetic substrates and implementation of mass spectrometry to elucidate enzyme specificities.

Acute effects of ethanol on left ventricular diastolic function

Transmitral flow velocities were measured by Doppler echocardiography in nine healthy men who ingested 1 g/kg of ethanol within one hour. The measurements were made before the first drink and every hour thereafter for three hours. The peak mean (SE) blood ethanol concentration was 21.4 (1.0) mmol/l. Each man was also studied after drinking fruit juice. Ethanol increased the heart rate but did not change the peak transmitral velocities, the normalised peak filling rate, the deceleration of early flow, or the duration of relaxation as measured from the second heart sound to the peak early diastolic velocity. The ratio of the peak atrial to the peak early diastolic velocity rose from 0.41 (0.03) to 0.44 (0.03) after ethanol but remained unchanged after juice. The difference between juice and ethanol was independent of changes in heart rate. The fluid balance was more negative in the ethanol experiment (-727 (114) ml v -107 (70) ml), suggesting a reduction in preload, and the ethanol-induced net loss of fluid correlated with the concomitant change in the velocity ratio. A moderate dose of ethanol causes a small acute increase of the ratio of the peak atrial to the peak early diastolic velocity of mitral flow in healthy subjects. Although this change indicates altered diastolic function of the left ventricle, most of it may result from the diuretic effect of ethanol. Any major impairment of ventricular relaxation seems unlikely.

An enzymatic kinetic method for the determination of 2'-deoxycoformycin in biological fluids

An analytical method for determination of 2'-deoxycoformycin (2'-DCF) concentrations in plasma and urine was developed based upon a modification of adenosine deaminase (ADA) inhibition assays described in the literature. The method involves the spectrophotometric monitoring of the rate of deamination of adenosine by the enzyme in the presence of various concentrations of the inhibitor 2'-DCF, and relating the deamination rate to the 2'-DCF concentration. In the course of developing the method, it was found that adenosine deaminase appears to lose activity after dilution with phosphate buffer (pH 7.2). Enzyme inactivation was found to occur mono-exponentially with time and, in order to accommodate for this inactivation, a method was developed for quantitating 2'-DCF which takes into consideration the relative activity of the enzyme in the incubation mixtures. The results obtained from the analysis of samples containing known concentrations of 2'-DCF were fitted to a three-dimensional standard surface by means of a nonlinear least-squares regression computer program. Quantitation of 2'-DCF in patient samples is accomplished by an ADA inhibition titration technique in which the spectrophotometrically determined absorbance change is related to the two independent variables, the concentration of 2'-DCF in the standards and the relative time of the analysis. As little as 1 ng/ml of 2'-DCF in plasma can be quantitated with the assay.

Increased susceptibility of fibroblasts from horses with severe combined immunodeficiency to growth inhibition by 2'-deoxyadenosine

The effect of adenosine, deoxyadenosine, guanosine, and deoxyguanosine on the growth rate of fibroblasts derived from normal horses, horses heterozygous for the severe combined immunodeficiency (SCID) trait (heterozygotes), and horses with SCID was studied. All four purines were found to inhibit growth in a dose-dependent manner, but only adenosine and deoxyadenosine were inhibitory at concentrations of less than 100 microM. No statistical difference in sensitivity to adenosine was detected between normal and SCID fibroblasts. Fibroblasts from SCID horses were, however, more sensitive to the growth inhibitory effects of deoxyadenosine than were fibroblasts from normal horses. Furthermore, following 24 hr of incubation with radiolabeled deoxyadenosine, radiolabeled deoxyATP concentrations were found to be twofold higher in SCID fibroblasts compared to those concentrations measured in normal fibroblasts cultured under identical conditions. Adenosine deaminase and S-adenosylhomocysteine hydrolase activities were normal in SCID fibroblasts. These findings suggest that SCID horses may have a defect in either transport or phosphorylation of deoxyadenosine, or in the utilization of deoxyATP.