A simple and sensitive radiochemical assay for plasma guanase

Area of Science:

• Biochemistry
• Enzymology
• Clinical Chemistry

Background:

• Plasma guanase (guanine aminohydrolase; EC 3.5.4.3) is an enzyme involved in purine metabolism.
• Accurate measurement of guanase activity is crucial for diagnosing certain liver conditions.
• Existing methods for guanase activity determination may lack sensitivity or simplicity.

Purpose of the Study:

• To develop a simple, sensitive radiochemical micro-assay for quantifying plasma guanase activity.
• To establish reference ranges for plasma guanase activity in healthy adults and children.
• To evaluate the diagnostic utility of the assay in patients with liver disease.

Main Methods:

• A radiochemical assay was developed utilizing 14C-labeled guanine as a substrate.
• The assay measures the conversion of labeled guanine to xanthine, catalyzed by guanase.
• Plasma samples from healthy adults, children, and patients with liver disease were analyzed.

Main Results:

• The developed assay demonstrated high sensitivity and simplicity for determining plasma guanase activity.
• Mean plasma guanase activity in healthy adults was determined to be 0.040 ± 0.09 nmol/h/mg protein.
• Significantly higher guanase activity was observed in children under 5 years of age.
• Adult patients with liver disease exhibited 3- to 7-fold increased plasma guanase activity compared to controls.

Conclusions:

• The novel radiochemical micro-assay provides a reliable method for assessing plasma guanase activity.
• Elevated plasma guanase levels are indicative of liver disease and developmental differences in children.
• This assay holds potential as a valuable biomarker in clinical diagnostics for liver function.