Development of a Spectrophotometric Method for
Monitoring Angiotensin-Converting Enzyme in Dairy Products
Julijana Tomovska*, S. Presilski, N. Gjorgievski,
N. Tomovska1, M. S. Qureshi2
and N. P. Bozinovska4
University St. Kliment Ohridski”, Faculty of
Biotechnical Science, Bitola, Macedonia; 1University “St.
Ciryl and Methodius”, Natural mathematics Faculty, Institute for
Chemistry, Skopje, Macedonia; 2Faculty of Animal Husbandry and Veterinary Sciences,
Agricultural University, Peshawar, Pakistan; 3METAROM,’Food
Flavouring & Colouring Industry, Sydney, Australia *Corresponding author: dzulitomovska@yahoo.com
Abstract
The angiotensin-converting enzyme (ACE) regulates
the levels of blood pressure through generation of angiotensin-II from
angiotensin-I. It is of great importance to have a reliable and yet simple
method for a quantitative determination ACE inhibitory peptides in whey of milk
products. A rapid, simple, sensitive and accurate spectrophotometric kinetic
method has been developed for determination of ACE inhibitory peptides, using
competitive inhibition. Samples of dairy product from the market were used for
the determination of ACE inhibitory peptides in whey. Holmquist’s kinetic method
was used for determining ACE inhibitory activity in blood serum and
Ronca-Testoni method was used for the determination of ACE inhibitory activity
in whey. Enzymatic inhibition activity was determined using 0.8 mmol/L FAPGG
(N-[3-(Furyl) –Acryloyl]-L-Phenylalanyl Glycyl Glycyne) as the substrate in 50
mmol/L Tris buffer at pH 8.2 at 370C and a standard serum containing
ACE. First, a solution of whey was mixed in a 1 to 10 ratio with serum
(elevation) containing high ACE activity. The enzymatic activity was determined
by monitoring the decrease in absorbance at 340 nm as result of hydrolysis of
the substrate. The concentration of ACE inhibitory peptides was determined from
a standard curve of inhibitor concentration versus percent of ACE inhibition.
The study suggests that the method possesses good
reproducibility and accuracy. The linear range enabled determination of high
enzymatic activity of ACE and all ACE inhibitory peptides from dairy products
act as competitive inhibitors.