Binds heparin and heparan sulfate with high affinity, but lacks heparanase activity. Inhibits HPSE, possibly by competing for its substrates (in vitro). Interacts with HPSE. Interacts with SDC1 (via glycan chains). Widely expressed, with the highest expression in brain, mammary gland, prostate, small intestine, testis and uterus. In the central nervous system, expressed in the spinal chord, caudate nucleus, thalamus, substantia nigra, medulla oblongata, putamen and pons. In the urinary bladder, expressed in longitudinal and circular layers of detrusor muscle. Found both in normal and cancer tissues. Expressed in the developing forebrain, diencephalon, midbrain, hind brain and spinal cord at Carnagie stage 16 (CS16, 6 weeks of gestation) and CS21 (8 weeks). The disease is caused by variants affecting the gene represented in this entry. Belongs to the glycosyl hydrolase 79 family.