In this method, the direct substrate N-[3 (2-furyl)-acryloyl]-L-phenyl-alanylglyclglycine (FAPGG) is hydrolyzed by plasma ACE to FAP and glycylglycine.
After incubation, 400 [micro]L of FAPGG substrate (0.80 mmol/L) was added to a cuvette with plasma and a 10-minute continuous recording of ACE activity was initiated.
On pools of sera from genotyped centenarians, the [K.sub.m] for FAPGG was 0.297 [+ or -] 0.035 for the D/D genotype, 0.288 [+ or -] 0.028 for the I/D genotype, and 0.325 [+ or -] 0.04 mmol/L for the I/I genotype, without statistical difference between them.
The [K.sub.m] for FAPGG was also determined in controls: on pools of sera from genotyped controls, the [K.sub.m] was 0.30 [+ or -] 0.02 mmol/L without statistically significant differences between the three genotypes or with the [K.sub.m] of centenarians sera, genotypically matched.
These results show that the [V.sub.max] of both HHL and FAPGG hydrolyses by human serum ACE are under genetic control in adults 20-70 years of age as well as in centenarians, and especially in relation with I/D polymorphism in an Alu sequence in intron 16 of the somatic ACE gene.