Mod 1 Enzymology Flashcards by Asherah Undug

Q

Polypeptide chains that differ in sequence but have similar enzymatic activity

A

Isozymes/ isoenzymes

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Q

Accelerates the rate of chemical reaction

A

Catalyst

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Q

Are protein catalysts utilized by essentially all mammalian cells in specific biochemical reactions

A

Enzymes

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Q

Catalysis on an insoluble surface

A

Heterogenous catalysis

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Q

Defines the capacity of protein catalysts to recognize and bind only one or a few molecules, the substrate excluding all others

A

Binding/ enzyme specificity

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Q

A substrate binding to an active site where it exhibits preformed steric and electronic complementarity to the shape and charge distribution of the substrate. No shape changes necessary for optimal binding

A

Lock and key model

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Q

Model that postulates an initial weak, flexible interaction of the substrate with groups in the enzymes ES binding site. It triggers a conformational rearrangement of the enzymes surface to enhance binding affinity

A

Induced fit model

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Q

Each enzyme has two names:

A

Practical/ trivial (e.g. Trypsin and papain)

Systemic name - unique numeric code designation and the nature of catalytic reaction

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Q

Identify the class described by its type of reaction catalyzed:

Oxidation- reduction reactions

A

Oxidoreductases

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Q

Identify the class described by its type of reaction catalyzed:

Transfer of functional groups

A

Transferases

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Q

Identify the class described by its type of reaction catalyzed:

Hydrolysis reactions

A

Hydrolases

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Q

Identify the class described by its type of reaction catalyzed:

Group elimination to form double bonds

A

Lyases

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Q

Identify the class described by its type of reaction catalyzed:

Isomerizations

A

Isomerases

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Q

Identify the class described by its type of reaction catalyzed:

Bond formation coupled with ATP hydrolysis

A

Ligases

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Q

Identify enzyme:

Catalyze transfer of phosphate group between phosphate and ADP to form creatine+ATP

Cofactor: magnesium

A

Creatine phosphokinase (CPK)

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Q

Primary tissue sources of which CK:

Plasma

A

CK-MM with

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Q

Primary tissue sources of which CK:

Brain, smooth muscle, prostate, thyroid, gut and lungs

A

CK-BB

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Q

Primary tissue sources of which CK:

Cardiac muscles

A

CK-MB (20-30%), CK-MM (70-80%)

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Q

Primary tissue sources of which CK:

Skeletal muscle

A

CK-MB, CK-MM (mostly)

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Q

Diagnostic application (CK):

Released during ischemia, injury, inflammation

increased in chronic myopathies, chronic renal failure, acute respiratory exertion

A

CK-MM

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Q

Diagnostic application (CK):

Indicated for brain trauma/ surgery, injury to smooth muscles, pts with malignancy: prostate CA, small cell lung CA, intestinal malignancies, transient increase after MI

A

CK-BB

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Q

Diagnostic application (CK):

Most commonly requested for detection of acute MI

Following MI: it rises proportional to extent of infarction
Appears in serum within 6 hrs after acute MI
Peak value: 12-24 hrs
Duration: 1.5 - 3 days

A

CK-MB

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Q

Normal values of total serum CK:

A

24-170 U/L for women

24-195 U/L for men

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Q

Marked total serum CK (> = 5x normal) can be seen in pts with:

A

Trauma (electrocution, surgery)
Athletic individuals (released during strenuous activities)
Muscular dystrophy
Chronic inflammation of muscle

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Mild/ moderate total serum CK (2 - 4x normal) can be seen in pts with:

Hyper or hypothermia Hypothyroidism After normal vaginal delivery Reye's syndrome

Forms that migrate electrophoretically in positions different from standard ones

Atypical isoenzymes

Catalyze formation of ATP and AMP from ADP Released from Erythrocyes

Adenylate kinase

Complex of CK-BB with antibody (IgG)

Macro CK Type 1

Oligometric variant of CK; mitochondrial (+) in serum - poor prognostic sign seen in pts with malignancies

Macro CK type 2

Digestive enzyme that acts extracellularly to cleave starch into smaller groups and to monosaccharides Major sources: salivary glands, exocrine pancreas

Amylase (diastase)

It is: Secreted by pancreozymin Readily cleared in urine Enters the duodenum at ampulla of vater via sphincter of oddi Liw levels found in fallopian tube, adipose tissues, skeletal muscle, small intestine

Pancreatic amylase

In acute pancreatitis, serum amylase levels rise within ________; remains high for a few days; return to normal in _______ days

Rise within 6-24 hours | Returns to normal in 2 -7 days

In a normal serum amylase with suspicion of pancreatitis measure:

24 hour urine amylase or serum lipase

Constrict pancreatic duct sphincter, decrease intestinal excretion and increased absorption in the circulation

Morphine administration

Optimal pH of 5.0 Common to tissues esp. prostate Small amounts in rbc, platelet, liver, spleen

Acid phosphatase (ACP)

Highly specific for prostatic ACP

Thymolphthalein monophosphate

Is measured typically by its ability to cleave phosphate groups at an acid pH. Used for diagnosis or monitoring of prostatic adenocarcinoma

Total ACP/ acid phosphate

Major applications of ACP:

Evaluation of prostate CA - not elevated in CA confined within prostate, BPH, prostatitis or ischemia of prostate Medico Legal evaluation in rape - vagina with little or no ACP, +ACP d/t seminal fluid

Widely distributed along the surface membranes of metabolically active cell Type of hydrolase Its most abundant isoforms are coded by a single gene on chromosome 1

Alkaline phosphatase

ALP has very high activity in:

Bones, liver, placenta, intestines, kidneys and WBC

Has been used to separate at least 6 different isoforms of ALP in healthy individuals

HPLC using weak anion exchange columns

Easiest and most common method for distinguishing ALP iso enzymes Heat serum at 53C for 15 minutes then compare with unheated sample

Heat fraction Bone ALP - extremely labile 10-20% retain original activity Liver and placental ALP - heat stable liver 30 - 50% retained Placenta will all retained

Chemical inhibitors of ALP: Blocks placental ALP Blocks liver and bone ALP

Urea - placenta | Phenylalanine - liver and bone ALP

Small,for the heart Functions in storage and transfer of oxygen from hemoglobin in the circulation to intracellular respiratory enzymes of contractile cells

Myoglobin

True or false: myoglobin is one of the first to diffuse out of ischemic muscle cells before CK?

True

Binds tropomyosin; governs excitation contraction coupling

Troponins

90% sensitivity for MI 8 hrs after onset of symptoms 95% specificity for MI 36% specificity to unstable angina

Troponin I

84% sensitivity for MI 8 hrs after onset of symptoms 81% specificity for MI 22% specificity to unstable angina

Troponin T

Have unique forms expressed in myocardial cells but not in other muscle types -presence in serum highly specific for Myocardial injury

Troponin I and troponin T

Troponin is released in two phases:

1. Initial damage (acute MI) peaks at 4-8 hours | 2. Sustained release from intracellular contractile apparatus - occurs up to days after acute event

General advantages of troponin T and I:

1. Released only ff cardiac damage 2. Present, remain elevated for a long time: troponin I is detectable up to 5 days Troponin T 7 to 10 days ff IM 3.very sensitive - measured by immunoassay

Catalyze conversion of lactate to pyruvate using NAD as co factor Present in cytoplasm of cells and all tissues in the body

Lactate dehydrogenase

Normal pattern of LD:

LD2>LD1>LD3>LD4>LD5

LD isozymes: | High in the heart, RBC and kidneys

LD1 and LD2

LD isoenzymes: High in skeletal muscle and liver

LD4 and LD5

LD activity can be measured either the:

Forward (lactate to pyruvate) or the reverse (pyruvate to lactate)

Diagnostic applications of LD: Markedly increased LD with normal AST, ALT and CK

Damage to biochemical dimple cells (RBC, WBC), kidney, lung, tumors

Diagnostic applications of LD: Increased LD and CK; increased AST > ALT

Cardiac or skeletal muscle injury

Diagnostic applications of LD: Increased AST snd ALT > LD

Transiently in liver disease

Used to confirm diagnosis of MI when CK isoenzyme analysis equivocal or after total CL and CK MB release has returned to normal

LD Peak 48-72 hours Returns to normal after 8 to 10 days

Used to estimate tumor mass including metastases

Total LD LD1 or LD2 increase in germ cell tumors ( tumor markers)

Flip LD1/LD2 ratio:

``` Extreme exercise Acute MI Hemolytic anemia Megaloblastic anemia Renal cortical disease (renal infarct) ```

Isomorphic pattern - Increased total LD, normal isoenzymes with tombstone pattern will lead to:

Diffuse tissue damage accompanied by shock and hypoxemia

Increased LD 2,3,4

Malignancy and tumor burden

Increased LD 3,4; decreased LD 1,2:

WBC tumors, pulmonary disease

Increased LD 4,5

Skeletal muscle injury, ischemic toxic hepatic injury