Key regulator of transforming growth factor beta (TGFB1, TGFB2 and TGFB3) that controls TGF-beta activation by maintaining it in a latent state during storage in extracellular space (PubMed:19651619, PubMed:19750484, PubMed:22278742). Associates specifically via disulfide bonds with the Latency-associated peptide (LAP), which is the regulatory chain of TGF-beta, and regulates integrin-dependent activation of TGF-beta (PubMed:22278742). Able to outcompete LTBP1 for binding to LAP regulatory chain of TGF-beta (PubMed:22278742). Controls activation of TGF-beta-1 (TGFB1) on the surface of activated regulatory T-cells (Tregs) (PubMed:19651619, PubMed:19750484). Required for epithelial fusion during palate development by regulating activation of TGF-beta-3 (TGFB3) (By similarity). {ECO:0000250|UniProtKB:G3XA59, ECO:0000269|PubMed:19651619, ECO:0000269|PubMed:19750484, ECO:0000269|PubMed:22278742}. This is the function of LRRC32 (leucine rich repeat containing 32, ENSG00000137507).