<prompt> In humans, rate limiting step of de novo pyrimidine synthesis is:Aspaate tanscarbamoylaseCarbamoyl phosphate synthetase-IIDihydro orotate dehydrogenaseOrnithine tanscarbamoylase  <response>: De-novo pyramidine synthesis Rate limiting step in mammals CPS II in bacteria Aspaate transcarbamoylase CPS I CPS II Rate-limiting enzyme of urea cycle Rate limiting step of pyrimidine synthesis Found in mitochondria Found in cytosol Uses ammonia as nitrogen source Uses glutamine as nitrogen source Requires N-acetylglutamate as positive allosteric activator Doesnt require N-acetylglutamate Hypoxanthine-guanine phosphoribosyltransferaseHP catalyzes salvage of the purine bases guanine and hypoxanthine into GMP and IMP. 