Product identification and kinetic studies of nucleotidyl cyclase activityin isolated chloroplasts by quantitative fast-atom bombardment mass spectrometry

While the natural occurrence of adenosine 3',5'-cyclic monophosphate and gu anosine 3',5'-cyclic monophosphate in higher plants is now well established , the existence in plants of specific nucleotidyl cyclase activities functi oning to synthesize these two cyclic nucleotides has been the topic of rece nt controversy. Here positive-ion fast-atom bombardment mass spectrometry i s used to unequivocally identify the products of the putative nucleotidyl c yclase activities in a membrane fraction from isolated spinach chloroplasts , and quantitative mass spectrometry is used in a study of enzymic reaction kinetics to determine the relevant kinetic parameters necessary for the el ucidation of the binding interactions between the substrates and the two en zymes, Copyright (C) 1999 John Wiley & Sons, Ltd.