Transporter Classification Database

The Transporter Classification Database ( TCDB ​​) is that of the International Union of Biochemistry and Molecular Biology ( IUBMB ) recognized classification for membrane transport proteins. The classification system was designed analogous to the EC- number system for the classification of enzymes.

The short form of arrangement has the form ABCDE, where lower case letters represent numbers. From left to right they are to transporter class, subclass and family, and subfamily and substrate (range). The classification of orthologs and paralogs is thus under the same number.