ID 6.2.2.2 DE oxazoline synthase. AN cyanobactin cyclodehydratase. AN cyanobactin heterocyclase. CA (1) ATP + L-amino acyl-L-seryl-[protein] = (S,S)-2-(C-substituted- CA aminomethyl)-4-acyl-2-oxazoline-[protein] + ADP + H(+) + phosphate. CA (2) ATP + L-amino acyl-L-threonyl-[protein] = (S,S)-2-(C-substituted- CA aminomethyl)-4-acyl-5-methyl-2-oxazoline-[protein] + ADP + H(+) + CA phosphate. CA (3) ATP + L-amino acyl-L-cysteinyl-[protein] = (1S,4R)-2-(C-substituted- CA aminomethyl)-4-acyl-2-thiazoline-[protein] + ADP + H(+) + phosphate. CC -!- Requires Mg(2+). CC -!- The enzyme, which participates in the biosynthesis of ribosomal CC peptide natural products (RiPPs), converts L-cysteine, L-serine and CC L-threonine residues to thiazoline, oxazoline, and methyloxazoline CC rings, respectively. CC -!- The enzyme requires two domains - a cyclodehydratase domain, known as CC a YcaO domain, and a substrate recognition domain (RRE domain) that CC controls the regiospecificity of the enzyme. CC -!- The RRE domain can either be fused to the YcaO domain or occur as a CC separate protein; however both domains are required for activity. CC -!- The enzyme can process multiple residues within the same substrate CC peptide, and all enzymes characterized so far follow a defined order, CC starting with the L-cysteine closest to the C-terminus. CC -!- The reaction involves phosphorylation of the preceding ribosomal CC peptide backbone amide bond, forming ADP and a phosphorylated CC intermediate, followed by release of the phosphate group. CC -!- In some cases the enzyme catalyzes a side reaction in which the CC phosphorylated intermediate reacts with ADP to form AMP and CC diphosphate. //