Figure 3.

Redox state of ²⁷²CXXC²⁷⁵ motif regulates CBS activity. A, the specific activities of wildtype CBS and of the CBS variants C272A, C275A, and C272A/C275A (double mutant) were measured using the methylene blue assay. The data points and error bars indicate the means ± S.D. (n = 4). ***, p < 0.001 versus wildtype CBS. B, the wildtype CBS protein and CBS variants were incubated without or with 10 mm DTT. The activities of these samples were determined using S-methylcysteine as the substrate in a 200-μl reaction solution containing 30 μm CPM fluorescent probe and 100 mm Hepes, pH 7.4. The data points and error bars show the means ± S.D. of three independent experiments. ***, p < 0.001 versus control; N.S., not significant.