Serine beta-lactamase-like protein LACTB, mitochondrial is an enzyme that in humans is encoded by the LACTBgene.[5][6] This gene encodes a 54 kDa protein sharing significant
sequence similarity to serine proteases of the penicillin binding protein and beta-lactamase superfamily occurring in bacteria.
[7] It is involved in the regulation of the metabolic circuitry. A causal association has been found between LACTB and obesity.[8] In breast cancer, LACTB has a tumor suppressor function by modulating lipid metabolism.[9]
LACTB shares sequence similarity to the beta-lactamase/penicillin-binding protein family of serineproteases that are involved in bacterial cell wall metabolism. The N-terminal 97 amino acid segment of LACTB does not form part of the conserved penicillin-binding protein domain and may therefore be responsible for organelle targeting.[7][10]
LACTB is widely expressed in different mammalian tissues, with the predominant expression in human skeletal muscle. It localizes in the mitochondrial intermembrane space.[10] LACTB can polymerize into stable filaments occupying the mitochondrial intermembrane space. These filaments are speculated to play a role in submitochondrial organization and therefore possibly affect mitochondrial metabolon organization.[10]
It has been found LACTB could cause obesity through gene co-expression analysis based on data integrated from multiple sources. This has been validated in vivo through LACTB overexpression in transgenic mice, which resulted in an obese phenotype.[8] LACTB has also been identified to be a tumor suppressor through its effect on mitochondrial phospholipid metabolism and modulation of cell differentiation state.[11]
^Keckesova et al. 2017. LACTB is a tumour suppressor that modulates lipid metabolism and cell state. Nature 543:681-686
^Lu JB, Yao XX, Xiu JC, Hu YW (January 2016). "MicroRNA-125b-5p attenuates lipopolysaccharide-induced monocyte chemoattractant protein-1 production by targeting inhibiting LACTB in THP-1 macrophages". Archives of Biochemistry and Biophysics. 590: 64–71. doi:10.1016/j.abb.2015.11.007. PMID26603571.
