Hepatic and Renal cysteine Sulfinic Acid Decarboxylase Activities in Cats Fed Different Levels of Dietary Protein and Taurine

In order to evaluate the dietary regulation of cysteine sulfinic acid decarboxylase (EC 4.1.1.29) in cats, acitivity and protein content of CSAD were assessed in the liver and kidney of cats fed different levels of dietary protein, with and without taurine. Four groups of cats were fed one of the follow diets for 5 weeks ; 20% protein and taurine- free diet(LP0T) ; 20% protein and 0.15% taurine diet(LPNT) ; 60% protein and taurine-free diet(HP0T); and 60% protein and 0.15% taurine diet (HPNT). CSAD activity was determined in the liver and kidney of cats by measuring 14C2 released form [1-14C]-L cysteine sulfinic acid. CSAD protein was quantified using an immunochemical method. CSAD activity was extremely low in cat tissues, among which kidney showed the highest activity which was 0.118$\pm$0.050, and 0.377$\pm$0.056 nmol.min-1.mg soluble portein-1 iin animals fed LP0T and HP0T, respectively. Even though renal CSAD protein content was 18~55% of the hepatic CSAD protein content, renal CSAD acitivity was 1.3~6.5 times of the hepatic CSAD activity . Renal CSAD acitivities of cats fed 60% protein were about 1.6~3.2 times those of animals fed 2.% protein , and hepatic CSAD activity was not significantly affected by the dietary level of protein. Taurine depletion significantly elevated both hepatic and renal CSAD activities above the values for cats having normal taurine status most probably as an adaptive response.