- A: a+b two layers
- X: a+b domain in D-aminoacid aminotransferase-like PLP-dependent enzymes
- H: a+b domain in D-aminoacid aminotransferase-like PLP-dependent enzymes
- T: a+b domain in D-aminoacid aminotransferase-like PLP-dependent enzymes
- F: Aminotran_4