A possible origin of RNA catalysis in multienzyme complexes.

Numerous attempts have recently been made to ascribe a preeminent role to RNA enzymes in primitive life systems. A model is proposed in which coenzyme-dependent RNA enzymes were initially organized in multienzyme complexes featuring (1) the continuous attachment of substrates to CoA-like carriers, as in fatty acid synthesis; and (2) the ordering of RNA enzymes via mRNA-like instructional strands. In this format, RNA enzymes would not have been required to recognize and specifically bind soluble substrates. The enzymes in this case may have required far less complexity than contemporary protein enzymes and thus less genetic information for their synthesis. An analogy is made between the proposed scheme and the protein translation mechanism, for which it may have been an evolutionary precursor.