Jørgensen P E, Nexø E, Poulsen S S, Almendingen M, Berg T
Department of Clinical Biochemistry, KH University Hospital, Aarhus, Denmark.
Growth Factors. 1994;11(2):113-23. doi: 10.3109/08977199409001053.
Epidermal growth factor (EGF) is synthesized as a precursor which is processed intracellularly to a 6 kDa EGF in the rat submandibular gland. This gland contains very high amounts of kallikrein-like enzymes, and the purpose of the present study was to examine whether any of five such enzymes, rK1, rK2, rK7, rK9 or rK10, can process the rat EGF precursor. Molecular weight forms of EGF, that were N- or C-terminally extended compared to submandibular gland EGF were obtained from rat urine. These extended forms of EGF were incubated with each of the enzymes for 24 h at 37 degrees C. Two enzymes, rK7 and rK10, were able to cleave N- and C-terminally extended EGF, releasing a form of EGF which eluted similarly to submandibular gland EGF upon gel filtration, and which was recognized both by antibodies against rat EGF and by the EGF receptor. One enzyme, rK1, cleaved C- but not N-terminally extended EGF. Neither rK2, nor rK9 cleaved the extended forms of EGF. In previous immunohistochemical studies rK1, rK7 and rK10 have all been demonstrated in the EGF containing cells of the rat submandibular gland. EGF and rK1 are also synthesized in the rat kidney but the present study demonstrated that EGF and rK1 are not colocalized in this organ. Based on the cleavage of the extended forms of rat EGF by rK1, rK7 and rK10 and on the fact that the enzymes are abundant and colocalized with EGF in the rat submandibular gland, we suggest that rK1, rK7 and rK10 can be involved in the processing of the EGF precursor in the rat submandibular gland.
表皮生长因子（EGF）最初是以一种前体形式合成的，在大鼠颌下腺中它会在细胞内被加工成6 kDa的EGF。该腺体含有大量类激肽释放酶，本研究的目的是检测五种此类酶（rK1、rK2、rK7、rK9或rK10）中的任何一种是否能够加工大鼠EGF前体。从大鼠尿液中获得了与颌下腺EGF相比在N端或C端有延伸的EGF分子量形式。将这些延伸形式的EGF与每种酶在37℃下孵育24小时。两种酶rK7和rK10能够切割N端和C端延伸的EGF，释放出一种在凝胶过滤时洗脱情况与颌下腺EGF相似的EGF形式，并且它能被抗大鼠EGF抗体和EGF受体识别。一种酶rK1能够切割C端但不能切割N端延伸的EGF。rK2和rK9都不能切割延伸形式的EGF。在先前的免疫组织化学研究中，rK1、rK7和rK10都已在大鼠颌下腺含EGF的细胞中被证实存在。EGF和rK1也在大鼠肾脏中合成，但本研究表明EGF和rK1在该器官中并非共定位。基于rK1、rK7和rK10对大鼠EGF延伸形式的切割以及这些酶在大鼠颌下腺中含量丰富且与EGF共定位这一事实，我们认为rK1、rK7和rK10可能参与大鼠颌下腺中EGF前体的加工过程。
