Nonterminal incorporation of adenosine monophosphate from adenosine triphosphate by chloroplast extract

Abstract

An enzyme system extracted from the grana fraction of spinach chloroplasts has been shown to catalyze the nonterminal incorporation of AMP from ATP into polynucleotide material. The same fraction can also carry out the incorporation of GMP and the respective nucleoside triphosphate inhibits the incorporation of AMP. Primer requirement is established and found to be ribopolynucleotide in nature. The loss of activity due to preincubation can be restored by RNA extracted from the enzyme preparation or poly A. Oligonucleotides of poly A are more effective in this respect. The incorporation of AMP is resistant to pancreatic DNase but susceptible to pancreatic RNase or T₂-RNase. The reaction product of AMP incorporation is acid precipitable, nondialysable and can be entrapped in poly T-cellulose. This is partly degraded by pancreatic RNase but completely by T₂-RNase. The nearest neighbor frequency analysis shows that while at least 90% of the AMP units occur next to AMP, the formation of random copolymer poly AG does not occur in the simultaneous presence of AM³²PPP and GTP as substrates. The reaction product can also enhance the incorporation of lysine by RNP and soluble enzyme systems.