Streptococcal extracellular NAD-glycohydrolase. Optimal temperature and activation by cysteine.

Streptococcal extracellular NAD-glycohydrolase (EC 3.2.2.5) exists in two distinct states with respect to the optimal reaction temperature. Bacteria produce the enzyme form with optimum activity at about 40 degress C. Probably due to oxygen action, the enzyme is converted to a form with optimum activity at 30 degrees C. Compounds of the type of cysteine restore the initial state. The conversions are accompanied by enzyme activity fluctuations.