Comparison of L-aspartate 4-carboxy-lyases of Cunninghamella elegans and Penicillium citrinum.

L-Aspartate 4-carboxy-lyase of Cunninghamella elegans and Penicillium citrinum has a pH optimum of 5.5. Maximal activity of both enzymes is obtained at 40 degrees C, and both are thermolabile. The Km of the C. elegans enzyme for L-aspartate is 25 mM, while that of the P. citrinum enzyme is 27 mM. The two enzymes are specific for L-aspartate. They are activated by pyridoxal 5-phosphate and a number of alpha-keto acids. The catalytic activity of both enzymes is stimulated by Co2+, Fe2+, Ni2+ and Mn2+ ions and inhibited by Zn2+ and Cu2+. Inhibition by iodoacetate and activation by SH-compounds suggest that sulfhydryl groups may participate in enzyme activity.