Evaluation Studies Enzyme Inhibition Studies Biology Essay

Dihydrofolate reductase is a omnipresent enzyme nowadays in all eucaryotic and procaryotic cells, playing a cardinal function in thymidine synthesis. It catalyzes the decrease of 7,8-dihydrofolate ( DHF ) to 5,6,7,8- tetrahydrofolate ( THF ) , using NADPH as cofactor.This reaction is an indispensable measure in the biogenesis of nucleotidic bases of DNA.1-3 Blockage of the DHFR enzyme causes cell decease as a consequence of DNA synthesis suppression. For this ground, DHFR is considered an first-class mark for planing antitubercular drugs.

All the synthesized derived functions of the substituted benzthiazole/benzimidazoles were evaluated for DHFR inhibitory activity utilizing the Dihydrofolate Reductase Assay Kit. The Kit is designed for the sensing of DHFR inhibitory activity and for testing DHFR inhibitors. It provides all the reagents required ( including a purified enzyme ) for the efficient sensing of DHFR activity and suppression in cell lysates, tissue homogenates, or column fractions of purified enzyme


Dihydrofolate Reductase ( DHFR ) – 0.1 unit

Assay Buffer 10X for DHFR -30 milliliter

Dihydrofolic acid ( DHFR substrate ) -3 X 10 milligram

Methotrexate ( DHFR inhibitor ) -2 X 10 milligram

NADPH ( Nicotinamide adenine dinucleotide phosphate reduced tetrasodium salt ) -25mg

Equipment required:

· Temperature controlled UV/visible spectrophotometer.

· 1 milliliter Quartz cuvette

· Ultrapure H2O:

Principle of check for DHFR activity

The check is based on the ability of Dihydrofolate reductase to catalyse the reversible NADPH-dependent decrease of dihydrofolic acid to tetrahydrofolic acid.


Dihydrofolic acid+NADPH+H+ Tetrahydrofolic acid+NADP+

At pH 7.5, the equilibrium of the reaction lies comparatively far to the right, and the reaction goes basically to completion in the forward way. The reaction advancement is monitored by the lessening in optical density at 340 nanometers.

Preparation of reagents:

1. Dihydrofolic acid ( substrate )

A 10 millimeter stock solution was prepared by keeping pH 7.5 by the add-on of 2.2 milliliters assay Buffer 10X to the dihydrofolic acid bottle ( i.e. , add 2.2 milliliters Assay Buffer 10X to 10 milligrams pulverization ) , and assorted good. Aliquot the 10 millimeters dihydrofolic acerb stock solution was taken and stored at -20 & A ; deg ; C. The staying fresh solutions was discarded on the same twenty-four hours.

2. 10 millimeter NADPH stock solution

A 10 milliliter suspension buffer was prepared by adding 0.2 milliliters Assay Buffer 10X to 9.8 milliliter H2O. 3 milliliter of the suspension buffer was added to the NADPH bottle. Mixed good and the solution was stored at -20 & A ; deg ; C.

3. Standard- ( Methotrexate-inhibitor ) stock solution

A 10 millimeter stock solution was prepared by adding 2.2 milliliter of Assay Buffer 10X to the bottle. Mixed good and stored it at -20 & A ; deg ; C.

4. Assay Buffer 10X

Assay Buffer 10X was diluted for DHFR ten crease in deionized H2O ( i.e. add 5 milliliters Assay Buffer 10X for DHFR to 45 milliliters H2O ) kept at room temperature.

5. Sample

All the synthesized compounds were prepared at a concluding concentration of 2 mg/ml reaction mixture.


The sum of DHFR supplied in the kit is about 0.1 units. The volume of the enzyme ( in milliliter ) to be used was calculated utilizing the expression, Volume ( milliliter ) = 1.5 X 10-3 X 1000/ ( units/mg protein ) Ten ( mg protein/ml ) . Harmonizing to the batch specific informations, the volume of enzyme to be used normally varies between 10-30 milliliter


Spectrophotometer was set at 340 nanometers and 22 & A ; deg ; C. Assay Buffer 10X was added to the trial microcentrifuge tubing and to which DHFR enzyme or the sample was besides added, assorted good. The synthesized compounds BTZ ( 1-13 ) and BIM ( 1-12 ) was besides added to the appropriate tubing, mixed good to which 6 µl of NADPH solution and 5 milliliter of dihydrofolic acid were added.The contents of the tubing were transferred to a 1 milliliter vitreous silica cuvette, assorted and instantly inserted the cuvette into the spectrophotometer. The kinetics plan was started instantly. The lessening in optical denseness ( DOD ) obtained were recorded as optical density at 340 nanometers. Consequences were tabulated and compared with standard methotrexate drug.

The optical density at 340 nanometers will diminish ( due to diminish in NADPH concentration ) . 10-20 milliliter of the supplied DHFR enzyme will normally give a additive incline during the 2.5 proceedingss of the sensing.

Activity computation

The lessening in DOD obtained during 2.5 min.as DOD/min was measured.

The activity was caluculated utilizing the expression: Units/mg

P = ( DOD/min.sample – ( DOD/min.blank ) X d/12.3 X V X milligram P/ml


DOD/minblank: DOD/min. for the space, from the spectrophotometer readings

DOD/minsample: DOD/min. for the reaction, from the spectrophotometer readings

12.3: extinction coefficient ( e, mM-1cm- ) for the DHFR reaction at 340 nanometers.

Volt: Enzyme volume in milliliter ( the volume of enzyme used in the check )

vitamin D: The dilution factor of the enzyme sample.

milligram P/ml: enzyme concentration of the original sample before dilution.

Units/mg P: – Specific activity in mmol/min/mg protein

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