Metazoan granulins are a family of cysteine-rich peptides of about 6 Kd which may have multiple biological activity. A precursor protein (known as acrogranin) potentially encodes seven different forms of granulin (grnA to grnG) which are probably released by post-translational proteolytic processing. Granulins are evolutionary related to PMP-D1, a peptide extracted from the pars intercerebralis of migratory locusts.