Chymotrypsin Lab Report

Enzymes combine with reactant molecules (substrate) and bind them closely to one another. The three-dimensional shape of the enzyme molecule must be complementary to the shape of the substrate.

Background and Introduction: Enzymes are proteins that process substrates, which is the chemical molecule that enzymes work on to make products. Enzyme purpose is to increase the rate of activity and speed up chemical reaction in a form of biological catalysts. The enzymes specialize in lowering the activation energy to start the process. Enzymes are very specific in their process, each substrate is designed to fit with a specific substrate and the enzyme and substrate link at the active site. The binding of a substrate to the active site of an enzyme is a very specific interaction. Active sites are clefts or grooves on the surface of an enzyme, usually composed of amino acids from different parts of the polypeptide chain that are brought together in the tertiary structure of the folded protein. Substrates initially bind to the active site by noncovalent interactions, including hydrogen bonds, ionic bonds, and hydrophobic interactions. Once a substrate is bound to the active site of an enzyme, multiple mechanisms can accelerate its conversion to the product of the reaction. But sometimes, these enzymes fail or succeed to increase the rate of action because of various factors that limit the action. These factors can be known as temperature, acidity levels (pH), enzyme and/or substrate concentration, etc. In this experiment, it will be tested how much of an effect

B. Catalysis occurs on a specific site on the enzyme (the active site). The active site is usually less than 5% of the surface area of the protein, and is always in a cleft. The rest of the molecule serves to present the active site in a three dimensional structure that is capable of binding substrate and catalyzing the reaction. Binding to a substrate is very specific, and involves ionic interactions, H bonds and van der Waals forces.

The independent variable in this investigation is pH. Each individual enzyme has it’s own pH characteristic. This is because the hydrogen and ionic bonds between –NH2 and –COOH groups of the polypeptides that make up the enzyme, fix the exact arrangement of the active site of an enzyme. It is crucial to be aware of how even small changes in the

After reviewing the basics of enzymes and catalysis, we take a dive into the wonderful

enable the substrate to bind to the enzyme and form the enzyme substrate complex and

J. Moldovan & B. Nilson, (2010), Lab 4 – Enzyme Kinetics, UBCO BIOL/BIOC 393, UBC Vista accessed Monday, November 8th, 2010.

Enzymes are proteins that act as a catalyst in bringing about specific biochemical reactions when met with particular substrates. Substrates will merge into a suitable area of the enzyme called an active site – this becomes the enzyme/substrate complex. Once the substrate is attached to the active site, the substrate will undergo a procedure where the substrate is modified and released as a product. There are different types of this that can occur, where either a chemical bond is broken in a substrate to produce two separate products; as in the ‘Induced-Fit’ model illustrated in figure 1.a. Chemical bonds can also be built between two substrates to produce a single product.

A Cofactor is another key component in some enzyme reactions. Cofactors are small inorganic molecules required for catalysis to occur in some reactions. Usually, cofactors are a metallic ion such as copper, zinc, iron, calcium, and so on. Cofactors may be bound tightly to the enzyme as permanent residents, or they may bind loosely and reversibly along with the substrate. A cofactor will enter the active site before the substrate and act as a helper to start the reaction. Some enzymes require the cofactor and some don’t.

The GLAT enzyme itself belongs to the histidine triad super family and is a member of branch III. This enzyme shows specific nucleoside monophosphate activity and is a homodimer with each monomer containing a single domain comprised of 6 α- helices and a β-sheet which is formed by 13 antiparallel and 1 parallel strand. The mechanism of this enzyme is described as having ping-pong kinetics with the following two steps. In the first step the active site histidine attacks R-phosphorus of UDP-glucose which displaces glucose-1-phosphate and forms a covalent intermediate. The second step involves the previously formed intermediate reacting with galactose-1-phosphate to displace the histidine and produce UDP-galactose. (Facchiano, 103-104).

Corporation, W. B. (2013). Introduction to Enzymes. Retrieved 2013 йил 27-2 from Worthington Biochemical Corporation: https://gateway.emmanuel.qld.edu.au/cvpn/aHR0cDovL3d3dy53b3J0aGluZ3Rvbi1iaW9jaGVtLmNvbQ/introbiochem/effectsph.html

Once the enzyme-substrate complex has been established, the enzymes amino acid side chains convert the substrate to the product. The products are then released from the enzyme. The enzyme remains unchanged by the first reaction, thus is free to catalyze another reaction (Mitchell 2006).

Abstract Enzymes are organic catalysts that can help speed up chemical reactions (enzymes function p57). There are very few exceptions, however all enzymes are proteins. Every enzyme is specific to a certain chemical reaction depending on its substrate as well as amount (enzyme function p57). Enzymes must maintain a specific structure so that they can work properly. If an enzyme's structure is changed by chemicals or heat it may not be able to function at all.

The way enzymes work is best described by the lock and key theory. Enzymes have a specifically shaped active site. This active site is highly specific to the shape of the substrate molecules, giving the substrates a surface to react on. This concept consists of the substrate ‘key’ being able to fit into the active site ‘lock’; here the substrate is held in place to proceed with the full reaction. Enzymes work best at their optimum temperatures and therefore homeostasis is important.

“Enzymes are proteins that have catalytic functions” [1], “that speed up or slow down reactions”[2], “indispensable to maintenance and activity of life”[1]. They are each very specific, and will only work when a particular substrate fits in their active site. An active site is “a region on the surface of an enzyme where the substrate binds, and where the reaction occurs”[2].