Studies on the control of lactate dehydrogenase isoenzyme activity from rat striated muscle by nad +

Abstract

1. 1. K m values of the five lactate dehydrogenase (E.G. I.I.I. 27, l-lactate : NAD-1-oxidoreductase) isoenzymes from striated muscle have been determined. 2. 2. Lactate was the variable substrate in the NAD+ concentration range 0.5–4.0 m M. 3. 3. LDH-1, LDH-2, LDH-3, and LDH-4 are activated by NAD+ 4. 4. The variability of the K m increases with the number of B-chains in the tetramer. 5. 5. On the other hand, LDH-5 activity is inhibited at higher NAD + concentrations. 6. 6. These results are discussed in comparison with those obtained previously with lactate dehydrogenase isoenzymes from rat brain.