Matrix metalloproteinase 23a (MMP23a) lacks the signal sequence found in other MMPs, suggesting that it may function intracellularly. The substrate for the enzyme has not been identified, but it is thought that the protein may play a role in reproductive processes. The MMP23A gene is part of a duplicated region of chromosome 1p36.3, which includes a second gene, MMP23B, which is almost identical.

The matrix metalloproteinases are secreted glycoproteins that are involved in the remodeling of the extracellular matrix. By analysis of the genomic region surrounding the duplicated genes CDC2L1 and CDC2L2, Gururajan et al. (1998) identified 2 novel matrix metalloproteinase genes, MMP23A, which they called MMP21, and MMP23B , which they called MMP22.