A Review on Spectrophotometric Methods for Measuring the Monophenolase and Diphenolase Activities of Tyrosinase

Abstract

Tyrosinase is a copper enzyme with broad substrate specifity toward a lot of phenols with different biotechnological applications. The availability of quick and reliable measurement methods of the enzymatic activity of tyrosinase is of outstanding interest. A series of spectrophotometric methods for determining the monophenolase and diphenolase activities of tyrosinase are discussed. The product of both reactions is the o-quinone of the corresponding monophenol/diphenol. According to the stability and properties of the o-quinone, the substrate is classified as four substrate types. For each of these substrate types, we indicate the best method for measuring diphenolase activity (among eight methods) and, when applicable, for measuring monophenolase activity (among four methods). The analytical and numerical solutions to the system of differential equations corresponding to the reaction mechanism of each case confirm the underlying validity of the different spectrophotometric methods proposed for the kinetic characterization of tyrosinase in its action on different substrates.

Substrate-dependent kinetics in tyrosinase-based biosensing: amperometry vs. spectrophotometry

“…Although the kinetics of tyrosinase have been mostly studied using spectrophotometry techniques [2], the application of the enzyme in biosensing usually focuses on electrochemical approaches. However, the electrochemical study of tyrosinase kinetics and its comparison and validation against spectrophotometric techniques have not been the subject of any specific study.…”

“…A variety of methods such as radiometry [1], ultraviolet-visible (UV-Vis) spectrophotometry [2], manometry [3], and electrospray ionization with ion trap mass spectrometry [4] has been developed to study enzyme kinetics, with UV-Vis spectrophotometry being the most commonly employed as it is non-invasive, sensitive, inexpensive and allows the enzymatic reactions to be monitored continuously.…”

“…Measurement of phenolic compounds is also important in medical diagnostics and food inspection. In the past, analysis was mostly based on the spectrophotometric [2] or chromatographic [9] approaches. Electrochemical detection of phenols is based on their electro-oxidation which requires high positive potentials.…”

Photosensitization of peptides and proteins by pterin derivatives

“…After the irradiation, the overall enzyme activity (oxidation of Tyr to L-dopachrome) was assayed according to the method of Pomerantz [46], which is based on the determination of L-dopachrome measured spectrophotometrically. The conversion of an inactive form of the catalytic site of the enzyme into an active form gives rise to a lag period before the reaction reaches maximal rate (Figure 3) [47]. Therefore, the enzyme activity (rate of formation of L-dopachrome, nM s −1 ) was determined in the linear phase by measuring the slope of the absorbance curve at 475 nm vs. time ( Figure 3).…”

Evaluation of the inhibition of mushroom tyrosinase and cellular tyrosinase activities of oxyresveratrol: comparison with mulberroside A

“…Melanin synthesis inhibition is mainly achieved via the inhibition of tyrosinase, a key enzyme of the synthetic pathway. Tyrosinase exhibits two enzymatic activities: it functions as a tyrosine hydroxylase that converts tyrosine to 3,4-dihydroxyphenylalanine (DOPA), and as a DOPA oxidase, which oxidizes DOPA to dopaquinone 11 . Melanin is synthesized in the melanosomes of melanocytes through a complex process.…”