Serine beta-lactamase-like protein LACTB, mitochondrial is an enzyme that in humans is encoded by the LACTB gene.

This gene encodes a protein from the large 39S subunit of the mitochondrial ribosome (mitoribosome). The encoded protein has some sequence similarity to prokaryotic beta-lactamases but most of the residues that are responsible for the beta-lactamase activity are not conserved between the two proteins. Two alternatively spliced transcript variants that encode different protein isoforms have been described for this gene. [provided by RefSeq, Nov 2010].