Cell surface hyaluronidase that mediates the initial cleavage of extracellular high-molecular-weight hyaluronan into intermediate-size hyaluronan (PubMed:28118600). Acts as a regulator of angiogenesis in embryos by mediating degradation of extracellular hyaluronan, thereby promoting VEGF signaling (PubMed:28118600). Acts as a regulator of heart development during myocardial and endocardial morphogenesis: involved in the looping stage of heart morphogenesis (PubMed:21896629). Stimulates migration of endocardial cells and increases both myocardial and endocardial fusion (PubMed:21896630). Involved in the restriction of endocardial cushions (ECs) formation to the atrioventricular canal (AVC) (PubMed:21896630). Also required for muscle fiber attachment (PubMed:27471259). Is very specific to hyaluronan; not able to cleave chondroitin sulfate or dermatan sulfate (By similarity). Random hydrolysis of (1->4)-linkages between N-acetyl-beta-D-glucosamine and D-glucuronate residues in hyaluronate. Expressed both maternally and zygotically. Expressed at the 2 cell stage. Ubiquitously expressed at the 22-somite stage. Expressed in the brain and head mesenchyme, otic vesicles, fin buds, caudal vein and the heart (both myocardial and endocardial cells) at 24 hours post fertilization (hpf). Embryos show defects in heart morphogenesis: while heart development is normal at the linear heart tube stage, cardiac looping is lost at later developmental stages (PubMed:21896629). Defects during the endocardial morphogenesis, characterized by the formation of ectopic atrioventricular canal in the ventricular myocardium and endocardium (PubMed:21896630). Maternal-zygotic mutants also display muscle fiber detachment, associated with impaired laminin organization and ineffective fibronectin degradation at the myotendinous junction (PubMed:27471259). Defects in angiogenesis, characterized by embryos with no venous sprouting (PubMed:28118600). Belongs to the CEMIP family.