Vitellogenesis-related ovary cathepsin D from Xenopus laevis: purification and properties in comparison with liver cathepsin D.
Cathepsin D was purified from ovaries of Xenopus laevis by both QAE-cellulose and pepstatin-Sepharose chromatography and then characterized and compared with Xenopus liver cathepsin D. Ovary cathepsin D appeared predominantly as a 43-kilodalton (kDa) molecular mass, as revealed by SDS-polyacrylamide gel electrophoresis, whereas the liver enzyme was obtained exclusively as a 36-kDa protein. The purified 43-kDa ovary enzyme cleaved vitellogenin limitedly to produce yolk proteins at pH 5.6. The specific activity of ovary cathepsin D was five to six times lower than that of the liver enzyme, as measured by hemoglobin-hydrolysis at pH 3, but the ovary enzyme was shown to be superior to the liver enzyme in terms of vitellogenin-cleaving activity, as examined at pH 5.6. Ovarian enzyme preparations contained variable amounts of 36-kDa species; this form was considered to be an autolytic product of the 43-kDa form arising during purification, because it was not detected in oocyte extracts but was generated by incubation of the purified 43-kDa enzyme alone in an acid solution. The conversion of the 43-kDa form by hepatic factors was accompanied by a marked increase in hemoglobin-hydrolytic activity.
Nakamura
K
K
Department of Biology, Faculty of General Education, Gifu University, Japan.
Yonezawa
S
S
Yoshizaki
N
N
D000818:Animals; D001329:Autolysis; D002402:Cathepsin D / Q000302:isolation & purification*; D005260:Female; D007527:Isoenzymes / Q000302:isolation & purification*; D008099:Liver / Q000201:enzymology*; D008970:Molecular Weight; D009865:Oocytes / Q000201:enzymology; D009928:Organ Specificity; D010053:Ovary / Q000166:cytology / Q000201:enzymology*; D014818:Vitellogenesis / Q000502:physiology*; D014982:Xenopus laevis / Q000378:metabolism*
D007527:Isoenzymes; D002402:Cathepsin D