<prompt> Rate limiting step in pyrimidine synthesisDihydro-orotaseOrnithine transcarbomoylaseAspaate transcarbomoylaseCarbamoyl phosphate synthase-I  <response>: Ref-D.M.Vasudevan 7e p506 Aspaatetranscarbamylase catalyses a committed step in pyrimidine metabolism by conveing carbamoyl phosphate into carbamoyl aspaate 