Enzymes

The amount of enzyme that causes utilization of substrate at the rate of: one micromole/minute:

international unit

Most specific enzyme test for acute pancreatitis:

lipase

Marker useful in the diagnosis of patients with congestive heart failure (CHF):

BNP

Inorganic ions such as calcium and chloride, necessary for enzyme activity:

activators

Where do the majority of enzymes detected in the plasma primarily function:

within cells

In an adult, a normal serum GGT level with an elevated serum ALP level may be suggestive of

bone disease

definition of enzyme

protein that acts as a catalyst

Primary tissue source of CK-MB:

cardiac muscle

Primary tissue source of CK-3:

skeletal muscle

Muscle protein that can be used to rule out AMI:

myoglobin

Enzyme that hydrolyzes triglycerides:

lipase

Enzyme that is the most sensitive indicator for liver damage from ethanol intake:

GGT

Protein that can be used to evaluate low level systemic inflammation and predict cardiovascular disease

CRP

CK-MB levels greater than ___ of total CK may be indicative of AMI:

6%

Enzyme that transfers an amino group from the amino acid alanine to a keto acid:

ALT (alanine aminotransferase)

When substrate is present in excess, what component acts in a rate limiting manner to control the speed of the reaction in a zero-order reaction:

enzyme concentration

List two conditions that can "physiologically" (normally) elevate serum ALP:

growth & third trimester pregnancy

What analyte is considered the most ideal cardiac marker providing early & sensitive detection as well as remaining elevated for several days following an AMI:

troponin

Enzyme that transfers a phosphate group from ATP to creatine to form creatine phosphate and ADP:

CK (creatine kinase)

The greatest activities of serum ALP and GGT are seen in:

obstructive jaundice

In the determination of LD (lactate dehydrogenase) at 340 nm, using pyruvate as a substrate, one actually measures the:

decrease in NADH

The substrate for lipase is:

triglycerides (olive oil is often used)

Enzyme that is grossly elevated in active muscular dystrophy; and rises early in myocardial infarction:

CK (creatine kinase)

As NADH is oxidized to NAD, it's absorbance at 340 nm:

decreases

Hydrolase enzyme cleaves phosphate ester bonds at an alkaline pH:

ALP (alkaline phosphatase)

Enzyme that catalyzes the conversion of lactate to pyruvate:

LD (lactate dehydrogenase)

_____amylase remains elevated longer than serum amylase:

urine

ALP (alkaline phosphatase)

Class: hydrolase

Tissue source: liver and bone

Ref range: 22-55 IU

Clin sig: hepatic disorders

Organic molecule required for full activity:

coenzyme (example - NAD/NADH)

Enzyme that would exhibit decreased levels upon exposure to pesticides:

pseudocholinesterase

The greatest activities of serum AST and ALT are seen in:

acute hepatitis

amylase (AMY)

Class: hydrolase

Tissue source: salivary glands and pancreas

Clin sig: acute pancreatitis

Requires calcium and chloride ions for activation

Rises in 8 hrs, peaks 12 - 24 hrs and returns to norm 3 - 5 days

Urine amylase remains increase longer, 10 days

Hydrolyses starch or carbs to maltose

The majority of CK is found in:

skeletal muscle

When an assay involves the continuous monitoring of change in absorbance as a function of time, the mode of analysis is termed:

kinetic

AST (asparatate amiontransferase)

Class: transferase

Tissue source: liver

Ref range: 8-36 IU

Clin sig: MI, hepatic and skeletal muscle disorders, up to 100x in viral hepatitis

Forms oxaloacetate and glutamate

transfers an amino group from aspartic acid to a keto acid

alanine aminotransferase (ALT)

Class: Lyase

Tissue source: liver

Ref range: 6-35 IU

Clin sig: hepatic disorders, more liver specific

Forms pyruvate and glutamate

Enzyme present in almost all tissues that may be separated by electrophoresis into five components is:

LD (lactate dehydrogenase)

Enzyme that may be useful in establishing the presence of seminal fluid in vaginal washings:

ACP (acid phosphatase)

transferases

enzymes that catalyze transfer of a specific group other than hydrogen

hydrolases

enzymes that catalyze cleavage of a variety of bonds by the addition of water

oxidoreductases

enzymes that catalyze oxidoreductive reactions between two substrates

In the determination of lactate dehydrogenase, lactate and NAD were incubated with the patient sample. As NADH was formed, the change in absorbance per unit of time was monitored. This is an example of a:

Continuous monitoring or kinetic assay (also referred to as rate measurement)

Statements that apply to zero-order kinetics:

enzyme is the only limiting factor

substrate is present in excess

concentration of enzyme is directly proportional to reaction rate

primary tissue sources CK-MB:

cardiac

primary tissue sources CK-3:

skeletal

alkaline phosphatase (ALP)

Class: hydrolase

Tissue source: liver and bone

Ref range: 22-55 IU

Clin sig: hepatic disorders

hydrolase enzyme cleaves phosphate ester bonds at an alkaline pH

gamma-glutamyl transferase(GGT)

Class: transferase

Tissue source: liver

Clin sig: hepatic disorders, alcoholism cirrhosis

aldolase (ALS, ALD)

Class: lyase

Tissue source: skeletal muscle

Clin sig: muscle disorders

lactate dehydrogenase (LD)

Class: oxioreductase

Tissue source: all tissues and liver

Ref range: 100-225 IU

Clin sig: MI, hepatic disorder, malignancies

Reversibly catalyzes the oxidation of lactic acid to pyruvic acid

Highest increases in pernicious anemia and hemolytic disorders

aspartate aminotransferase (AST)

Class: transferase

Tissue source: liver

Ref range: 8-36 IU

Clin sig: MI, hepatic and skeletal muscle disorders, up to 100x in viral hepatitis

Forms oxaloacetate and glutamate

transfers an amino group from aspartic acid to a keto acid

The presence of CK-BB activity on a CK electrophoresis pattern is most likely found in a patient suffering from:

severe head injury or stroke

apoenzyme

protein portion of the complex

holoenzyme

apoenzyme + the coenzyme, entire enzyme complex

coenzyme

organic non protein required for enzyme activity

ALP: markedly increased

ALT: slightly increased

AST: slightly increased

GGT: markedly increased

obstructive jaundice (gall stones)

What may cause denaturation of the enzyme structure:

severe pH alteration (too acidic or too basic)

significant increase in temperature beyond optimal

presence of an inhibitor substance

In an adult, a normal serum GGT level with an elevated serum ALP level may be suggestive of:

bone disease

may be associated with the creatine kinase isoenzymes:

CK-MB is >6% of total CK in AMI

fastest moving during electrophoresis

CK-1 referred to as CK-BB

This illustration represents the change in absorbance at 340 nm over a period of 8 minutes in an assay for lactate dehydrogenase. True statements about this figure include:

nonlinearity after 6 minutes is due to substrate exhaustion

Which of the following tests, if negative 2 - 3 hours following a suspected AMI, would rule out a possible AMI:

myoglobin

If a total CK is 560 IU and the CK-MB is 18 IU, what is the CK relative index:

18/560 = 3.2%

Which enzyme is thought to be involved in the protection of erythrocytes from hemolysis?

G6PD

Which of the following products are formed from the forward reaction catalyzed by ALT?

pyruvate and glutamate

Lactate dehydrogenase (LD) exhibits elevated serum levels in many disorders. The disorder in which LD demonstrates an elevation up to 50 times the upper reference limit is:

megaloblastic anemia

LD is released from the rbcs during hemolysis.

Which one of the following enzymes catalyzes the transfer of an amino group to alpha-ketoglutarate with the formation of oxaloacetate and glutamate?

AST (aspartate aminotransferase)

Altered production due to genetic defect usually leads to _____

decreased serum level

Serum or plasma from a heparinized sample are used in the assay for alkaline phosphatase. Why is heparin the only acceptable anticoagulant to use if using plasma for the alkaline phosphatase test?

Other anticogulants bind magnesium which is a required cofactor for activation

Which of the following enzyme assays used 4-nitrophenyl phosphate as the substrate?

ALP