and the biosynthesis pathway diverges depending on ..
Deoxyribose, or more precisely 2-deoxyribose, ..
The key molecule in the synthesis of the pyrimidine ribonucleotides isuridine monophosphate (UMP), as it is the final product of the six-stepsynthesis pathway and from which CTP is subsequently derived. Thepyrimidine ring, in the form of dihydroorotate, is formed first (note that thisis not the case for the pyrimidine bases) following attachment toribose-5-phosphate.
Pentose Phosphate Pathway - an overview | …
We expected that the first step, in which PRPP is synthesized, would besubject to regulation because of the prominence of PRPP in other biosyntheticreactions, including that of pyrimidine nucleotides. Increasing levels of ADPand GDP have a negative feedback effect on the enzyme Ribose phosphatepyrophosphokinase. The enzyme catalyzing the second step of the pathway,Amidophosphoribosyl transferase, is inhibited by all of the adenine and guaninenucleotides, the adenine nucleotides binding to one inhibitory site on theenzyme and the guanine nucleotides to another separate site. This enzyme is also"activated" by the increase in the level of PRPP and this is called a"feedforward activation".