Biology The presence of quinones prevents infection of microorganisms because it is toxic to them Danyk, H, Quinones are produced by the oxidation of phenolic compound of catechol.
Social and Educational Studies Volume issue 4 1: Research in this area is often conducted with purified enzymes and extrapolated to in vivo conditions. The specificity constant, Km Michaelis- Menten constantVmax catalytic powerIC50 and Ki inhibition constant expresses the efficiency of an enzyme as a catalyst.
These parameters are usually determined for enzyme catalysis and inhibition study. In this work we propose a classroom experiment for its determination using polyphenol oxidase PPO enzyme from banana.
In addition, inhibition experiment was carried out by L-cysteine and p-aminobenzene sulfonamide which is classical PPO inhibitors. Although there were a few variations in the kinetic parameters results among students, the students generally carried out the program successfully by correctly identifying inhibition type.
The inquiry-based problem solving approach of this curriculum facilitates an understanding of the basic concepts of biochemistry and its application. Introduction Characterization of enzyme kinetics today plays an essential role in important areas such as medical diagnostics, proteomics research, or even enzyme inhibition based biosensors for environmental monitoring.
Of all subjects covered in a general biochemistry textbook enzyme kinetics and inhibition are perhaps the one topic that has the most tangible relevance to everyday life . Inhibitors of enzymes are used as pharmaceutical agents in human and veterinary medicine as well as herbicides and pesticides .
However, as instructors may know, students typically find this topic difficult. Some reasons for this, as well as one possible solution involving computer simulations, have been addressed by Gonzalez-Cruz et al. Students at our university offer 4-hr elective biochemistry lab for a week.
For the above reasons, I conducted an experiment that allowed students to understand enzyme kinetics much better after carrying out an offered lab experiment in two week.
Harlen and Wake  also indicated that practical work in the classroom increases the effectiveness of teaching science by providing students with hands-on experience with science and allowing them to infer the theory behind the experimentation . Many different enzymes are used in undergraduate laboratory kinetics experiments published in standard laboratory texts.
These enzymes include tyrosine hydroxylase [5, 6] alkaline phosphatase  and lactate dehydrogenase LDH . Polyphenol oxidase is chosen in this study since it catalyzes a reaction that is often familiar to students. Many students have seen the browning of fruits and vegetables and thus have an immediate connection this enzyme.
Students also have the opportunity to see this enzyme again during the everyday life.
In addition, polyphenol oxidase may be a good model enzyme for teaching practical classes ranging from beginning level to more advanced biochemistry courses, in order to demonstrate important principles of kinetic studies and parameter determination Vmax, Km, Ki .
In fact, a review of 20 general biochemistry textbooks commonly used in undergraduate and medical school courses revealed that the two methods namely Lineweaver-Burk and Eadie Hofstee showed the determination of the Michaelis constant Km and maximal velocity Vmax [1, 9].
The aim of this work is to design newly practical experiment for biochemistry laboratory to learning enzyme kinetics for undergraduate students. Polyphenol oxidase enzyme extract was prepared from banana.
The students determined Km and Vmax values using catechol and 4-methylcatechol as substrate with Lineweaver-Burk graphs. PPO, often called tyrosinase, is an enzyme that synthesizes in many species of plants and fungi. It is homologous to mammalian tyrosinase, an enzyme involved in melanin formation.
PPO is a metalloenzyme which contains two active-site copper ions that are essential for enzymatic activity. It catalyzes a redox reaction in which various phenolic compounds are oxidized Figure 1ultimately leading to the production of dark-colored pigment molecules which cause the familiar browning of vegetables, fruits, and mushrooms as they age or when they are bruised.
For more information, see the reviews by Yoruk and Marshall  and Mayer . Hence, a suitable protocol is suggested for determination of kinetic parameters in universities. This protocol facilitates understanding of students to important of inhibitor as pharmaceutical agents in human and veterinary medicine as well as herbicides and pesticides, another important enzyme biotechnology.
This protocol allows students to explore the biotechnology used in a variety of fields and to understand the concepts of enzyme kinetics.Linoleic acid is a doubly unsaturated fatty acid, occurring widely in plant glycosides.
It is an essential fatty acid in mammalian nutrition and is used in the biosynthesis of prostaglandins and cell membranes. The temperature will not affect the activity of the catechol oxidase. Ha The enzyme will function best at temperatures closest to the optimal temperature, so temperatures at both extremities of 40 degrees Celsius will have lower to no reaction rates.
This study focused on the effect of pH on the activity, thermokinetics and inhibition of polyphenol oxidase (PPO) from honeydew peach pulp with (+)-catechin as the substrate.
The optimum pH for the PPO activity was around –, and the optimum temperature was pH dependent and it was 40 °C at pH while 30 °C at pH The ascorbic acid oxidase is only slightly active below pH and above , thus having a very limited range of activity, re- stricted to the acid side of the pH scale.
The best pH level for catechol oxidase based on the results was neutral, or a pH of 7. The results showed that the catechol oxidase in the pH 7 had the highest absorbency after . In this study, the effect of temperature on activity in presence of catechol and pyrogallol was plombier-nemours.com polyphenol oxidase activity in green small cherry tomatoes extract two pH optimum were observed, respectively at and 8, that probably belong to.