11. In azamacrocycle chemistry, diacetylpyridines can undergo the same Schiff base condensation with N1-( 3-aminopropyl ) propane-1, 3-diamines. 12. The Schiff base , which is conjugated to the enzymes pyridinium ring is the focus of the coenzyme activity. 13. Lysine 69 on ornithine decarboxylase ( ODC ) binds the cofactor pyridoxal phosphate to form a Schiff base . 14. Ornithine displaces the lysine to form a Schiff base attached to ODC, which decarboxylates to form a quinoid intermediate. 15. It also functions as the nucleophile during hydrolysis of the enzyme-product Schiff base , leading to the release of pyruvate. 16. For this step, the Schiff base must be heated to ~ 250 �C for the ring closure to occur. 17. For example, using aniline as a nucleophilic catalyst, a less populated protonated carbonyl becomes a highly populated protonated Schiff base . 18. A Schiff base forms between secologanin's aldehyde-group and tryptamine s amine group, from which Glu309 deprotonates tryptamine s carbon 2. 19. Lys296 is conserved in all known opsins and serves as the site for the Schiff base linkage with the chromophore. 20. Figure 1 : General mechanism of acetoacetate decarboxylase, proceeding through a Schiff base intermediate and producing acetone and carbon dioxide
