CONVERSION OF HIGH MOLECULAR WEIGHT HUMAN EPIDERMAL GROWTH FACTOR (hEGF)/UROGASTRONE (UG) TO SMALL MOLECULAR WEIGHT hEGF/UG BY MOUSE EGF-ASSOCIATED ARGININE ESTERASE*
Human epidermal growth factor (hEGF) has previously been isolated from urine and appears to be identical to β-urogastrone (UG), an inhibitor of stimulated gastric acid secretion. A high molecular weight (HMW) form of hEGF/UG has recently been found in human urine which is fully immunoreactive but is less bioactive as measured by receptor binding activity. A specific arginine esterase, the EGF-binding protein from mouse submandibular glands, was capable of cleaving HMW-hEGF to yield a small molecular weight (SMW)-hEGF with full immunoreactivity and bioactivity, whereas trypsin produced a SMW-hEGF with much less bioactivity. SMW-hEGF produced by the arginine esterase appeared to be immunologically, biologically (both by receptor binding and mitogenic activity) and chromatographically similar to highly purified hEGF. These data suggest that HMW-hEGF may play a precursor role in the biosynthesis of hEGF/UG in man.