<P> De novo pathways do not use free bases : adenine ( abbreviated as A ) , guanine ( G ) , cytosine ( C ) , thymine ( T ) , or uracil ( U ) . The purine ring is built up one atom or a few atoms at a time and attached to ribose throughout the process . Pyrimidine ring is synthesized as orotate and attached to ribose phosphate and later converted to common pyrimidine nucleotides . De novo synthesis enzymes are predicted to be present as large multienzyme complexes , although this hypothesis has yet to be thoroughly proven . </P>
<P> De novo pathways do not use free bases : adenine ( abbreviated as A ) , guanine ( G ) , cytosine ( C ) , thymine ( T ) , or uracil ( U ) . The purine ring is built up one atom or a few atoms at a time and attached to ribose throughout the process . Pyrimidine ring is synthesized as orotate and attached to ribose phosphate and later converted to common pyrimidine nucleotides . De novo synthesis enzymes are predicted to be present as large multienzyme complexes , although this hypothesis has yet to be thoroughly proven . </P>
where does de novo synthesis of purine occur
where does de novo synthesis of purine occur
attached to ribose
attached to ribose