Kininase enzymes of cat eye tissues

Conference · Sat Mar 01 00:00:00 EST 1986 · Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States)

OSTI ID:5322063

Ryan, J W; Anderson, D R

Eye tissues contain kininase activities, including an angiotensin converting enzyme (ACE)-like activity. The authors have begun further to characterize the ACE-like activity and to examine for another reputed kininase, carboxypeptidase N (CPN). Homogenates of tissues of 6 cat eyes and paired plasmas were assayed for ACE using 3 acyl-tripeptide substrates, /sup 3/H-benzoylated F-A-P, F-G-P and A-G-P (respectively, BFAP, BFGP and BAGP). CPN was assayed using /sup 3/H-benzoyl-A-R. All eye tissues and fluids contained ACE- and CPN-like activities. The ACE activity was clearly owing to ACE: relative values of Kc/Km for BFAP, BFGP and BAGP were those for pure ACE (2.213, 1.751 and 1.0); reactivities with inhibitors were as expected (Ki for captopril, MK 422 and RAC-X-65: 2.7, 0.62 and 0.31 nM). EDTA inhibited both ACE and CPN (I/sub 50/'s: 43 and 47 ..mu..M). CPN activity was inhibited by 2-mercaptomethyl-3-guanidinoethylthiopropionate (Ki 2.4 nM). However, distributions of the two enzymes differed markedly. Virtually all tissues contained ACE at specific activities higher than that of plasma. Specific activities appeared to be a function of tissue vascularity (for choroid, ciliary body, iris, retina and plasma: 7.31, 2.57, 1.98, 1.53 and 0.21 pmol/mg protein). Only iris contained more CPN that did plasma (23.0 v. 7.21 pmol/mg protein). The tissue distribution of ACE is that expected for an endothelial-associated enzyme. Plasma may be the major source of CPN in eye tissues other than iris.

• Research Organization: Univ. of Miami School of Medicine, FL
• OSTI ID: 5322063
• Report Number(s): CONF-8604222-; TRN: 86-028374
• Journal Information: Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States), Vol. 45:3; Conference: 70. annual meeting of the Federation of American Society for Experimental Biology, St. Louis, MO, USA, 13 Apr 1986
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
PEPTIDE HYDROLASES
ENZYME ACTIVITY
CATS
ENZYME INHIBITORS
EYES
RETINA
TRACER TECHNIQUES
TRITIUM COMPOUNDS
ANIMALS
BODY
BODY AREAS
ENZYMES
FACE
HEAD
HYDROLASES
ISOTOPE APPLICATIONS
LABELLED COMPOUNDS
MAMMALS
ORGANS
SENSE ORGANS
VERTEBRATES
550201* - Biochemistry- Tracer Techniques