FIGURE 2.

Time course of the changes in carnosine, ADP, and AMP concentration during carnosine synthesis. A chicken enzyme preparation (11 μg of protein) purified by chromatography on DEAE-Sepharose, Q-Sepharose, and Superdex 200 was incubated for 0, 60, and 120 min with 1 mm MgATP in the absence (empty symbols) or presence (filled symbols) of 3 mm l-histidine, 1 mm β-alanine, as well as 750 × 10³ cpm of [³H]β-alanine. ΔADP values were calculated by subtracting ADP concentration values in the absence of β-alanine and l-histidine from the corresponding values in the presence of these substrates. The formation of radiolabeled carnosine was determined after chromatographic separation from β-alanine. ADP and AMP were determined by HPLC. The figure shows the mean of two experiments performed under similar conditions and yielding similar results (less than 5% variation).