Figure 6.

Proposed mechanisms for direct utilization of ammonia detected in the A. glabripennis midgut. Several methods for re-incorporating ammonia produced through nucleotide or amino acid deamination reactions into amino acid and nucleosides were reconstructed based on the presence of unigenes in the A. glabripennis midgut transcriptome. Ammonia can be directly integrated into glutamine by glutamine synthetase, which can subsequently be converted into glutamate by microbial-derived glutamate synthase detected in the A. glabripennis midgut metagenome. Glutamate could subsequently be converted into either proline by a series of reactions catalyzed by γ-glutamyl kinase, dehydrogenase, aminotransferase, and pyrroline-5-carboxylate or aspartate via transaminase, respectively. Furthermore, aspartate can be converted into inosine, which can be directly used for synthesis of purine nucleotides or asparagine via asparagine synthetase. *Microbial in Origin. ¹Succinylaminoimidazole carboxamide ribotide synthase. ²Aminoimidazole carboxamide ribotide transformylase.