ANALOGS OF TAURINE AS INHIBITORS OF THE PHOSPHORYLATION OF AN SIMILAR-TO-20K MOLECULAR-WEIGHT PROTEIN PRESENT IN A MITOCHONDRIAL-FRACTION OF THE RAT RETINA

It has been previously demonstrated that taurine inhibits the phosphor ylation of an similar to 20 K apparent molecular weight protein presen t in the mitochondrial fraction of the rat retina (Lombardini, 1991). In the present studies, various analogues of taurine were tested for t heir inhibitory activity on the phosphorylation of this similar to 20 K protein. The most potent analogues were (+/-)trans-2-aminocyclopenta nesulfonic acid (TAPS) and 1,2,3,4-tetrahydroquinoline-8-sulfonic acid (THQS) which were approximately 21 and 7 times more potent than the p arent compound, taurine. Median-effect plots were used to calculate th e inhibitory median effect and combination index values for the combin ed effects of taurine and taurine analogues. From these studies, it wa s determined that the inhibitory taurine analogues were antagonistic t o taurine when used in combination with taurine to inhibit the phospho rylation of the similar to 20 K apparent molecular weight protein. It was also concluded that: 1) the distance between the nitrogen and sulf ur atoms in the taurine structure was important for inhibitory activit y; 2) if the nitrogen atom is either within or attached to an unsatura ted ring structure the inhibitory potency was significantly decreased, and 3) if both the sulfur and nitrogen atoms are present within the r ing structure the analogue has no activity.