NRPS-like enzyme with an unusual domain architecture that converts back glycine betaine to choline via a 2-step reduction mechanism, and thereby can be an alternative source of choline (PubMed:31061132). Permits direct reutilization of endogenously stored glycine betaine for on-demand biosynthesis of choline and choline derivatives, including phospholipid phosphatidylcholine (PC) which has an essential role in maintaining membrane integrity and functionality, or choline-O-sulfate, a mean for intracellular sulfate storage (PubMed:31061132). Glycine betaine is activated by the adenylation (A) domain, and transferred to the thiolation (T) domain (PubMed:31061132). Movement of the phosphopantetheine arm to the thioester reductase domain R1 then allows thioester reduction by NADPH of glycine betainoyl thioester to glycine betaine aldehyde, which is in turn reduced to choline by the aldehyde reductase domain R2 (PubMed:31061132). The tetramethylammonium ion, which mimics the head group of glycine betaine, acts as a competitive inhibitor of ATRR A domain, whereas the potency decreased by three orders of magnitude with dimethylammonium (PubMed:31061132). Choline is a mixed inhibitor for both glycine betaine reductase and aldehyde reductase activity but more potent in competition against glycine betaine in the first reduction step (PubMed:31061132). Therefore, choline could act as a feedback inhibitor to regulate ATRR enzymatic activity (PubMed:31061132). The lowered binding affinity of choline to R2 favors the release of choline after glycine betaine aldehyde reduction to avoid direct product inhibition (PubMed:31061132). The NRPS-like protein ATRR has an unusual domain arcitecture (A-T-R1-R2), with the adenylation domain A activating and thioesterifying glycine betaine which is then channeled through the phosphopantetheine arm of the T domain, the thioester reductase domain R1 reducing glycine betainoyl thioester to glycine betaine aldehyde, and the aldehyde reductase domain R2 converting glycine betaine aldehyde into choline. Severely impairs the hyphae growth and conidiation at high level glycine betaine (PubMed:31061132). Exhibits a choline-auxotroph character, when the phosphatidylethanolamine N-methyltransferase choA is also deleted (PubMed:31061132). Belongs to the NRP synthetase family.