Figure 7.

Aβ42-to-Aβ40-converting activity in adult mouse brain cortex is lower than that in embryonic brain cortex. (A) Synthetic Aβ42 protein (40 μM) was incubated with 20 μg of cortex lysate from 17-day-old embryos or 3-month-old mice. Aβ40 and Aβ42 were detected by Western blotting. (B) Quantification of Aβ40 converted from Aβ42. Embryo cortex exhibited higher Aβ42-to-Aβ40-converting activity than adult cortex. Values represent the mean ± SEM; n = 3; **p < 0.001, by unpaired two-tailed Student’s t test. (C) Ang-converting activity was measured by incubating 2 μg of total protein of cortex lysate from 17-day-old embryos or 3-month-old mice with the synthetic o-aminobenzoyl peptide substrate for 24 h at 37°C. Values represent the mean ± SD; n = 3; NS, not significant, by unpaired two-tailed Student’s t test. (D) Western blots of 20 μg of total protein of cortex lysate from 17-day-old embryos or 3-month-old mice were probed with a polyclonal anti-ACE antibody. (E) 20 μg protein of cortex lysate from 17-day-old embryos or 3-month-old mice were de-glycosylated and incubated with synthetic Aβ42. Aβ40 and Aβ42 were detected by Western blotting.