Characterization of the aspartate carbamoyltransferase fragment generated by protease action on the pyrimidine-3 gene product of Neurospora crassa.

The molecular weight of the fragment of aspartate carbamoyltransferase (carbamoylphosphate: L-aspartate carbamoyltransferase, EC 2.1.3.2) of Neurospora crassa following proteolysis was found to be 1.0-10(5) (aspartate carbamoyltransferase-L). It differs from the native form of the enzyme (aspartate carbamoyltransferase-N, 6.5-10(5)) in several respects. It has a lower V, has a much greater affinity (approx. 3-fold) for L-aspartate, and is strongly activated by glycine. Both forms of aspartate carbamyoltransferase have a pH optimum of approx. 9.5, and they exhibit similar affinities for carbamoyl phosphate.