Introduction: Enzymatic reactions have played arguably one of the most important roles in the evolution of complex cellular life. By using proximity interactions to achieve thermodynamic favorability, enzymes are able to catalyze reactions that would have never occurred on a reasonable human time scale. This paper will highlight the importance of an enzyme aptly named “dihydrofolate reductase”, which has an integral role in an essential metabolic pathway. Spanning across thousands of organisms, this particular enzyme is utilized for the recycling of dihydrofolate (figure 1), a useful byproduct generated from thymidylate synthase catalysis. Figure 1: Structure of dihydrofolate (DHF)
Superficially, dihydrofolate Reductase (which I will abbreviate DHFR for the remainder of this paper) catalyzes the reduction of dihydrofolate to 5,10-methylene tetrahydrofolate (figure 2) using NADPH (figure 3) as the hydride donor.
Figure 2: Proposed Mechanism Figure 3: Structure of nicotinamide adenine dinucleotide phosphate (NADPH)
A subsequent enzyme called thymidylate synthase then
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Prokaryotic cells tend to be rich in NADP+, allowing bacterial DHFR to always be in proximity to its cofactor10. One would expect NADP+ to be released after the hydride transfer to dihydrofolate, however this is not the case. The rate limiting step for the entire mechanism is actually the association/dissociation of NADPH following hydride transfer. Once NADPH is bound, tetrahydrofolate is released and DHFR may immediately begin reducing the next dihydrofolate11. This “constant priming” is made possible by higher dissociation rates of NADP+ when THF is bound, and higher dissociation rates for THF when NADPH is bound10. In this way, we can see that self-allosteric regulation occurs based on the NADPH concentration in the cellular
Data from Table 1. confirms the theory that as the concentration of glucose increases so will the absorbance of the solution when examined with the glucose oxidase/horseradish peroxidase assay. Glucose within the context of this assay is determined by the amount of ferricyanide, determined by absornace, which is produced in a one to one ratio.1 Furthermore when examining the glucose standards, a linear calibration curve was able to be produced (shown as Figure 1). Noted the R2 value of the y = 1.808x - 0.0125 trend line is 0.9958, which is statistically considered linear. From this calibration curve the absorbance values of unknowns samples can be compared, and the correlated glucose concentration can then be approximated.
In the lab, Inhibiting the Action of Catechol Oxidase we had to investigate what type of enzyme inhibition occurs when an inhibitor is added. Catechol oxidase is an enzyme in plants that creates benzoquinone.Benzoquinone is a substance that is toxic to bacteria. It is brown and is the reason fruit turns brown. Now, there are two types of inhibitors, the competitive inhibitor and non-competitive inhibitor. For an enzyme reaction to occur a substrate has to bind or fit into the active site of the enzyme. In competitive inhibition there is a substrate and an inhibitor present, both compete to bind to the active site. If the competitive inhibitor binds to the active site it stops the reaction. A noncompetitive inhibitor binds to another region
The isomerization procedure was done in order to create dimethyl fumarate from dimethyl maleate. Dimethyl maleate and dimethyl fumarate are cis and trans isomers, respectively. This procedure was done via a free radical mechanism using bromine. The analysis of carvones reaction was done in order to identify the smell and optical rotation of the carvone samples that were provided. The odor was determined by smelling the compound and the optical rotation was determined using a polarimeter.
Data table 1 Well plate Contents Glucose concentration A 3 drops 5% sucrose + 3 drops distilled water Negative B 3 drops milk+3 drops distilled water Negative C 3 drops 5% sucrose +3 drops lactase Negative D 3 drops milk +3 drops lactase 15+ E 3 drops 20% glucose +3 drops distilled water 110 ++ Questions B. In this exercise, five reactions were performed. Of those reactions, two were negative controls and one was a positive control.
In this experiment the enzyme peroxidase and the substrate hydrogen peroxide were not mixed initially, instead they were both placed in separate tubes and were incubated at a specific temperature, to prevent hydrogen peroxide from undergoing any reaction with peroxidase until they both acquire the required temperature.
Living organisms undergo chemical reactions with the help of unique proteins known as enzymes. Enzymes significantly assist in these processes by accelerating the rate of reaction in order to maintain life in the organism. Without enzymes, an organism would not be able to survive as long, because its chemical reactions would be too slow to prolong life. The properties and functions of enzymes during chemical reactions can help analyze the activity of the specific enzyme catalase, which can be found in bovine liver and yeast. Our hypothesis regarding enzyme activity is that the aspects of biology and environmental factors contribute to the different enzyme activities between bovine liver and yeast.
One of the most primitive actions known is the consumption of lactose, (milk), from the mother after birth. Mammals have an innate predisposition towards this consumption, as it is their main source of energy. Most mammals lose the ability to digest lactose shortly after their birth. The ability to digest lactose is determined by the presence of an enzyme called lactase, which is found in the lining of the small intestine. An enzyme is a small molecule or group of molecules that act as a catalyst (catalyst being defined as a molecule that binds to the original reactant and lowers the amount of energy needed to break apart the original molecule to obtain energy) in breaking apart the lactose molecule. In mammals, the lactase enzyme is present
The affects of pH, temperature, and salt concentration on the enzyme lactase were all expected to have an effect on enzymatic activity, compared to an untreated 25oC control. The reactions incubated at 37oC were hypothesized to increase the enzymatic activity, because it is normal human body temperature. This hypothesis was supported by the results. The reaction incubated to 60oC was expected to decrease the enzymatic activity, because it is much higher than normal body temperature, however this hypothesis was not supported. When incubated to 0oC, the reaction rate was hypothesized to decrease, and according to the results the hypothesis was supported. Both in low and high pH, the reaction rate was hypothesized to decrease, which was also supported by the results. Lastly, the reaction rate was hypothesized to decrease in a higher salt concentration, which was also supported by the results.
The purpose of this experiment was to see if phenylthiourea (PTU) is a non-competitive or competitive inhibitor. Catechol, a phenolic compound found in the potato extract used will play the part of the substrate. Competitive inhibitors are known to bind to the active site of an enzyme and mimic the job of a substrate. This in turn causes the substrate to compete for a position at the active site and increase the concentration of substrate but the inhibitor is still at a constant level. If PTU were a competitive inhibitor the test tube carrying the extract would turn dark brown. Non- competitive inhibitors are known to bind on the enzyme and prevent the substrate from attaching
Mader, S. S. (2010). Metabolism: Energy and Enzymes. In K. G. Lyle-Ippolito, & A. T. Storfer (Ed.), Inquiry into life (13th ed., pp. 105-107). Princeton, N.J: McGraw Hill.
its work. It is called the “lock and key” hypothesis. Lock in the enzymes. key: The substrate of the.
In biology class, we were learning about enzymes. Enzymes are proteins that help catalyze chemical reactions in our bodies. In the lab, we were testing the relationship between the enzyme catalase and the rate of a chemical reaction. We predicted that if there was a higher percentage of enzyme concentration, then the rate of chemical reaction would increase or it would take less time. We placed 1 ml of hydrogen peroxide into four depressions. Underneath the first depression, we place 1 ml of 100% catalase and make 50% dilution with 0.5 ml of water. We take 50% of that solution and dilute with 0.5 ml of water and we repeat it two more times. there were four depressions filled with catalase: 100%, 50%, 25% , 12.5 % with the last three diluted
This is made possible by the use of enzymes. Enzymes essentially work within the cells and their ability determined as a result of their specificity brought about by the shapes from the amino acid sequences (Daniel and Danson 2740).
Madar, Sylvia S., & Windelspecht, Michael. (2014). Inquiry into Life, Metabolism: Energy & Enzymes (pp. 104-107). New York: McGraw Hill.
Enzymes are necessary for life to exist the way it does. Enzymes help our bodies carry out chemical reactions at the correct speed. Catalase is one such enzyme, “Catalase is a common enzyme found in nearly all living organisms exposed to oxygen (such as bacteria, plants, and animals). It catalyzes the decomposition of hydrogen peroxide to water and oxygen”.\(Wikipedia). In other words catalase speeds up the breaking down of hydrogen peroxide, which is a byproduct of reactions in our body. Hydrogen peroxide is very common in our body but, “If it were allowed to build up it would kill us”(Matthey).This shows how necessary enzymes such as catalase to life. Without enzymes reactions that take place in our body could be affected greatly. In our