D-ribose has demonstrated significant enhancing abilities in replenishing deficient cellular energy levels following myocardial ischemia, does the metabolic pathway differ from that of D-glucose? It seems to be more ready for catabolism for the ischemic tissue in the congestive heart failure!!
Dr. Bader,
It depends what you mean by "replenishing deficient cellular energy levels".
One of the characteristics of ischemia in any tissue (but especially heart) is a net loss of 5'-nucleotides. To replenish these nucleotides (either by de novo synthesis or by salvage synthesis), the cell needs phosphoribosyl pyrophosphate (PRPP) as one of the staring materials. Ribose is phosphorylated to ribose-1-phosphate, which is then metabolized to PRPP via PRPP synthetase. Most tissues (aside from liver) have low levels of PRPP synthetase, so the process is slow; however, addition of ribose will enhance nucleoside salvage synthesis in heart two-fold or even more.
Glucose, on the other hand, uses glycolysis and the Krebs cycle to increase ATP levels (and, by proxy, levels of other 5'-nucleotides) via chemiosmosis and the mitochondrial F1-ATPase. This increase is dependent on the parent molecules for these nucleotides (ADP, CDP, GDP, UDP, TTP) being present. Glucose will not enhance the levels of these parent molecules, only see to the addition of the final phosphate (an increase in energy charge, but not total cellular levels).
So, ribose and glucose are really doing different things from a cellular point of view.
Cheers,
T. Geisbuhler
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