Aspartate Transcarbamylase

Aspartate Transcarbamylase from Leishmania donovani

Leishmania donovani is a protozoal pathogen that belongs to the kinetoplastida order. Unlike in other eucaryotic systems, the first three enzymes of the de novo pyrimidine biosynthetic pathway are not components of a multifunctional protein system. The three enzyme activities in the crude extract were separated on a Sephacryl S-200 column. Aspartate carbamoyltransferase (EC 2.1.3.2) has been pu...

Proton Magnetic Relaxation of Aspartate Transcarbamylase

Nuclear magnetic relaxation methods were used to investigate the interaction of the inhibitor succinate with aspartate transcarbamylase from Escherichia coli. Over the pH range 7 to 9, the dissociation constant for succinate remains less than the inhibitor concentration used for most of this work (0.05 M). As a result, the enzyme predominantly exists in a single “gross” conformational state. Su...

Functionally important arginine residues of aspartate transcarbamylase.

The reaction of phenylglyoxal with aspartate transcarbamylase and its isolated catalytic subunit results in complete loss of enzymatic activity (Kantrowitz, E. R., and Lipscomb, W. N. (1976) J. Biol. Chem. 251, 2688-2695). If N-(phosphonacetyl)-L-aspartate is used to protect the active site, we find that phenylglyoxal causes destruction of the enzyme's susceptibility to activation by ATP and in...

Interaction of aspartate transcarbamylase with regulatory nucleotides.

Carbamyl phosphate-aspartate transcarbamylase activity in tumors.

The enzyme carbamyl phosphate-aspartate transcarbamylase catalyzes the transfer of the carbamyl group from carbamyl phosphate (CP) to L-aspartate ($). Preliminary experiments with a series of six relatively advanced azo dye-induced hepatomas indicated that hepatoma tissue had a higher CP-aspartate transcarbamylase activity than did liver from normal animals. Experiments are reported here in whi...