Exam 4: Enzymes

Enzymes are…

biological protein catalysts

Write or say the formula for enzyme-catalyzed reactions. Below are the components.

product, substrate, enzyme

Substrate —> Enzyme —> Product

Enzymes are measured by what?

Activity

How does Substrate Concentration influence enzymes?

increases rate enzymatic of reaction

How does pH influence enzymes?

changing enzyme shape & electrical charge

How does temperature influence enzymes?

increases the velocities (speed) of chemical reactions

Activators, or coenzymes increase the rate of an enzymatic reaction.

Cofactors

Various substances that can decrease the rate of reaction.

Inhibitors

Inhibitor binds to the ES complex to form an enzyme substrate complex but doesn’t result in a product.

Uncompetitive inhibition

Substance is similar to the normal substrate and competes with the substrate for the bind or active site of the enzyme.

Competitive

Inhibitor structurally different than the substrate and binds to an allosteric site on the enzyme molecule.

Non- competitive inhibition

Enzyme Classification:

Responsible for oxidase reduction

Oxidoreductase

Enzyme Classification:

Transfers Carbon, Nitrogen or Phosphorus containing groups— from a donor molecule to a acceptor.

Transferases

Enzyme Classification:

Cleavage of bonds by adding water.

Hydrolases

Enzyme Classification:

Cleavage of carbon-carbon, carbon-nitrogen & carbon to ‘S’ bonds.

Lyases

Enzyme Classification:

Racemization of optical or geometric isomers

Isomerases

Formation of bonds b/n C and O, S, N coupled to hydrolase high energy phosphate.

Ligases

Enzyme Clin Sig.

Associated with hepatocellular disease or damage to hepatocytes.

AST and ALT

CK-1;

Brain and CNS

CK-2

Heart muscle

CK-3

Skeletal & Heart muscle

An aminotransferase that catalyzes the deamination of

alanine. Greatest concentration within the cytoplasm of the liver + liver specific issues.

Alanine Aminotransferase (ALT)

Reference range for ALT is…

6-37 u/L

With excessive (really HIGH) ALT what could be the patients health issue? What about moderate levels of ALT?

Hepatitis. Obstructive liver disease.

Catalyzes the interconversion of amino acids and α-oxoacids by the transfer of amino groups. Elevations occur mostly in the heart, liver, skeletal muscle and kidneys related diseases/conditions…

Aspartate Aminotransferase (AST)

Related to high/elevates levels in pediatric/adolescence and pregnancy(placenta)…?

Alkaline Phosphatase (ALP)

Reference range for AST is…

5-30 u/L

Within clinical testing with the use of patient serum for AST and ALT, what should be avoided?

Hemolysis (destruction of RBC)

In which liver disease is the DeRitis ratio (AST: ALT) usually less than 1?

Viral hepatitis

Cirrhosis

Alcoholic hepatitis

All of the above

Viral hepatitis

Organic cofactors that commonly have a structure related to vitamins:

Holoenzymes

Coenzymes

Prosthetic groups

Substrate

coenzymes

Present in all body tissue, richest in cell membranes and alkaline nature. Found highest in hepatobiliary diseases; hepatobiliary obstruction and biliary tract disorders.

Alkaline Phosphatase (ALP)

Reference range for Alkaline Phosphatase (ALP)…

44-147 u/L

Alkaline phosphatase(ALP) enzyme…what disease?

pt. 1 : muscle, brain, bone or pancreas

pt. 2: Obstructive liver disease, Hepatitis, Renal failure or Pancreatitis

Bones; Obstructive Liver

Alanine aminotransferase(ALT) enzyme…

Liver (specific)

Acid Phosphate (ACP) enzyme…

Prostate

Creatine Kinase (CK) enzyme…

Heart

Amylase enzyme…

a. prostate

b. Pancreas

c. Liver, bone, muscle

pancreas

Lactate Dehydrogenase (LDH) enzyme…

Hemolysis (Liver + Heart)

Aspartate aminotransferase(AST) enzyme…

Heart, Liver, Muscle

Gamma-glutamyl transferase (GGT) enzyme…

RBC

NOT property of enzymes:

a. Small amounts of the enzyme required because the enzyme is used over

and over again

b. Enzymes are not altered or consumed during the reaction

c. Enzymes alter the equilibrium constant required for the reaction

d. Enzymes accelerate the speed at which a chemical reaction reaches

equilibrium

Enzymes alter the equilibrium constant required for the reaction

All of the following are factors influencing enzyme action except:

a. pH

b. Temperature

c. Color

d. Cofactors

e. Inhibitors

Color

Most of clinically significant enzymes function at a pH of _________ and a

temperature of ____________.

a. 7-8, 37ºC

b. 2-3, 37ºC

c. 7-8, 25ºC

d. 2-8, 25ºC

7-8 ; 37C

A heat-labile protein portion of enzyme is called the ______________, which

requires a _______________ for full catalytic activity.

a. Holoenzyme; cofactor

b. Apoenzyme; coenzyme

c. Holoenzyme; substrate

d. Apoenzyme; inhibitor

Apoenzyme; coenzyme

Fill in the Blank:

_______________________________ is defined as amount of enzyme that

produces 1µmol of product per minute under standardized conditions of

temperature, pH, substrate, and activators.

International Unit

Increases in the MB fraction of CK is associated with:

a. Liver disease

b. Bone disease

c. Kidney failure

d. Myocardial infarction

Myocardial infraction

CK-1, CK-2, and CK-3 are examples of:

a. Transport proteins

b. Isoenzymes

c. Hetroenzymes

d. Inhibitors

isoenzymes

The recommended storage temperature for the preservation of activity for MOST

enzymes is:

a. 0ºC

b. 4ºC

c. 25ºC

d. 37ºC

4C

Which of the following blood tests is used to determine acute pancreatitis?

a. Acid phosphatase

b. Uric acid

c. Amylase

d. Alkaline phosphatase (ALP)

amylase

In enzyme kinetics, the reaction rate dependent of substrate concentration is

known as:

a. Zero-order kinetics

b. First-order kinetics

c. Second-order kinetics

d. Double-order kinetics

First-order kinetics

Serum chemistry results on a 35 year old male are:

Results Ref. Range

AST 100 U/L 4-34 U/L

ALT 185 U/L 5-40 U/L

ALP 85 U/L <165 U/L

GGT 22 U/L 5-24 U/L

These results are consistent with a possible diagnosis of _______________

a. Hemolytic anemia

b. Hepatitis

c. Biliary obstruction

d. Myocardial infarction

Hepatitis

When measuring enzyme activity, if the instrument is operating 5ºC lower than

the temperature prescribed for the method, how will the results be affected?

a. Lower than actual

b. Higher than actual

c. Varied, showing no particular pattern

d. No effect

Lower than actual

The properties of enzymes are CORRECTLY described by which of the following

statements?

a. Enzyme activity is not altered by heat denaturation

b. Enzymes are protein catalysts of biological origin

c. Enzymes are stable proteins and unaffected by pH changes

d. Enzymes affect the rate of a chemical reaction by raising the activation

energy needed

Enzymes are protein catalysts of biological origin

Wrong about enzyme inhibition:

a. Inhibitors are various substances that can decrease rate of reaction

b. Competitive inhibitors are substances similar to normal substrate

c. Uncompetitive inhibitors bind to an active site of the enzyme

d. Non-competitive inhibitors are structurally different from substrate

Uncompetitive inhibitors bind to an active site of the enzyme

Incorrect about ALT & AST methodologies:

a. The decrease in absorbance at 340 nm as NADH is oxidized to NAD +

measured

b. In both measurements, a temperature of 37ºC used for incubation

c. In both measurements, a two-step reaction principle is used

d. The increase in absorbance at 340 nm as NADH is oxidized to NAD +

measured

The increase in absorbance at 340 nm as NADH is oxidized to NAD +

measured

That portion of an enzyme which is separated from its cofactor is called a(n):

a. Holoenzyme

b. Isoenzyme

c. Coenzyme

d. Apoenzyme

Apoenzyme

18. Given the following data, what is the most likely disease state?

AST = 75 (2-25)

ALT = 118 (2-23)

LD = 220 (<140)

ALP = 841 (28-68)

GGT = 150 (21-40 U)

a. Intoxication

b. Hemolytic disease

c. Biliary duct obstruction

d. Bone disease

Biliary duct obstruction

A reaction is in ___________ kinetics when the reaction rate depends only on

enzyme concentration.

a. Zero-order

b. First-order

c. Second-order

d. Mixed-order

Zero-order

Which of the following blood tests is used in determination of prostate cancer?

a. Acid phosphatase

b. Alkaline phosphatase (ALP)

c. Alanine aminotransferase (ALT or SGPT)

d. Creatinine

Acid phosphate (ACP)

Place them correctly.

MK 1:

MK 2:

MK 3:

1. BB (bone)

2. Heart muscle

3. Skeletal & Heart muscle

An enzyme that breaks down starch to simple sugars:

Amylase.

Phosphatase.

Lipase.

Kinase.

Amylase