DID PRIMITIVE MICROORGANISMS USE NONHEM IRON PROTEINS IN-PLACE OF NADP/

Nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinuc leotide phosphate (NADP) are of universal occurrence in living organis ms and play a central role in coupling oxidative with reductive reacti ons. However, the evidence that the origin and early evolution of Life occurred at high temperatures (>95 degrees C) is now strong, and at t hese temperatures some modern metabolites, including both the reduced and oxidized forms of these coenzymes, are unstable. We believe there is good evidence that indicates that in the most primitive organisms n onhem iron proteins carried out many or all of the functions of NAD/P( H). This has important implications for the way in which investigation s of archaebacterial metabolism are conducted.