OAT and Gyrate atrophy of choroid and retina: This crystal structure suggests a mechanism for the specific ω-transaminase function of OAT [58]: the α-amino and α-carboxy groups of Orn are anchored to Y55 and R180 respectively (mutations Y55S and R180T on these two residues cause loss of OAT activity, and lead to gyrate atrophy [64,65]); thus only the δ-amino group can approach the reactive Schiff adduct of K292-PLP.