Radiolabelled substrates for angiotensin converting enzyme

Journal Article · Wed Jan 01 00:00:00 EST 1986 · Adv. Exp. Med. Biol.; (United States)

DOI:https://doi.org/10.1007/978-1-4684-5143-6_58· OSTI ID:6704556

Chung, A Y; Ryan, J W; Ryan, J P; Ryan, U S

Six (3H)benzoyl-tripeptides were prepared and tested as substrates for angiotensin converting enzyme. Each was prepared first as its (4-iodo)-benzoyl-analog, and an atom of 3H per molecule was introduced by catalytic dehalogenation in 3H2-gas. Kinetic parameters were measured at 37 degrees C using as buffer 0.05 M Hepes, pH 8.0 containing 0.1 M NaCl and 0.6 M Na2SO4. When the substrates were used at concentrations far below their respective Km values, fractional rates of substrate utilization per unit time for constant enzyme concentration were direct function of respective second order rate constants (Kc/Km). Although absolute values of Kc/Km differed for human enzyme as opposed to rabbit enzyme, relative values of Kc/Km were virtually identical. Similarly, relative rates of substrates utilization during passage through lungs of anesthetized rats were similar to relative values of Kc/Km measured in vitro. Thus, there is now a range of ACE substrates usable, in vitro and in vivo, under conditions of first order enzyme kinetics, conditions under which values of V/Km and Ki can be measured directly.

• Research Organization: Univ. of Miami, FL
• OSTI ID: 6704556
• Journal Information: Adv. Exp. Med. Biol.; (United States), Journal Name: Adv. Exp. Med. Biol.; (United States)
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
ENZYMES
BIOCHEMICAL REACTION KINETICS
ANGIOTENSIN
PEPTIDES
RABBITS
RATS
SUBSTRATES
TRACER TECHNIQUES
TRITIUM COMPOUNDS
ANIMALS
CARDIOVASCULAR AGENTS
DRUGS
GLOBULINS
ISOTOPE APPLICATIONS
KINETICS
LABELLED COMPOUNDS
MAMMALS
ORGANIC COMPOUNDS
PROTEINS
REACTION KINETICS
RODENTS
VASOCONSTRICTORS
VERTEBRATES
550201* - Biochemistry- Tracer Techniques