The Stereochemical Course of Nucleotidyl Transfer Catalysed by NAD Pyrophosphorylase

Abstract
NAD pyrophosphorylase catalyes nucleotidyl trasfer from adensone (R′‐[α‐17O]triphosphate to nicotinamide monocucledotide with inversion of configuration at the α‐P giving (S‐[17O]NAD+. The simplest interpretation of the observation is that the adenyly group is trasferred directly from ATP to the co‐substrate by an ‘in line’ mechanism. It is also shown that snake venom phosphodiesterase hydrolyses NAD+ regio‐specifically at the adenylyl terminus of the pyrophosphate bond.