Essential extracellular matrix (ECM) protein that influences cell rearrangements. May act by modulating metalloproteinases action during organogenesis. Able to non-competitively inhibit procollagen N-proteinase, an ADAMTS metalloproteinase. Homooligomer; disulfide-linked. During embryogenesis it first appears in the extracellular matrix during gastrulation and early mesoderm development at sites where basement membranes do not subsequently form. Later, migrating hemocytes prominently produce it together with other ECM components, in basement membranes that underlie epithelia and envelop muscles and emerging organs. At various life stages, it can be synthesized by other cells, such as those of the fat body, and it also occurs in a few, circumscribed regions of relatively amorphous ECM. Isoform E is specifically expressed in ECM of heart and proventriculus. Isoform C is a major component of transitory ECM deposit in the early embryo. Isoform F is a major component of the basement membrane during embryogenesis. Expressed throughout development and is prominent in adult basement membranes. Appears after 4 hours of embryogenesis, peaks at 8-12 hours and remains thereafter. N-glycosylated. Sulfated. Belongs to the papilin family.