β-Defensin 4A is a membrane-active cationic peptide that functions in inflammation and innate immune responses. There are at least 30 β-Defensins, which are distinguished from α-Defensins by the connectivity pattern of their three intermolecular disulfide bonds. Members of the Defensin family are highly similar in protein sequence. This gene encodes Defensin, DEFB4;, which has broad-spectrum antimicrobial activity and may play an important role in innate epithelial defense. They are highly expressed in skin and tonsils, and to a lesser extent in trachea, uterus, kidney, thymus, adenoid, pharynx and tongue. β-Defensin 4A has low expression in salivary gland, bone marrow, colon, stomach, polyp and larynx. No expression in small intestine. The 45 amino acid mature human BD3 shares 38% and 33% amino acid sequence identity with mouse and rat BD3, respectively.

Prosaposin (PSAP) gene mutations, affecting saposin B (Sap-B) domain, cause a rare metachromatic leukodystrophy (MLD) variant in which arylsulfatase A (ARSA) activity is normal. The human prosaposin gene (PSAP) was previously localized to 10q21-->q22 by isotopic in situ hybridization using a human prosaposin cDNA as a probe. Using fluorescence in situ hybridization with a mouse genomic prosaposin fragment as probe, confirms the localization of PSAP and precisely maps it to band 10q22.1. PSAP/Prosaposin Protein, Human, Recombinant (His) is expressed in HEK293 mammalian cells with His tag. The predicted molecular weight is 57.9 kDa and the accession number is A0A024QZQ2.

Defensins are cationic peptides. It is an important ingredient of the innate immune system. β-defensins are expressed on some leukocytes and epithelial surfaces. Four human β-Defensins have been identified to date: BD-1, BD-2, BD-3 and BD-4. β-defensins contain a six-cysteine motif, they forms three intra-molecular disulfide bonds. β-defensins are also chemoattractant towards immature dendritic cells and memory T cells. The β-defensin proteins are expressed as the C-terminal portion of precursors; they are released by proteolytic cleavage of a signal sequence.