Clinically important enzymes
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Amylase is sourced from
the pancreas and salivary glands; splits starch into sugars at alpha linkages.
(amylase method) Amyloclastic
Amylase acts on starch substance. Use iodine to determine amount of substrate remaining.
The oldest amylase method or classic reference method is
Sacharogenic, determines amount of sugar produced (product)
The method in which amylase hydrolyzes insoluble dye/starch complex increasing absorbance is
Chromogenic; increase in color intensity proportional to amylase activity
The amylase method which includes the coupling of several enzyme systems by a continuous monitoring technique is called.
Kinetic method (340nm) optimal pH 6.9
Which enzyme hydrolyzes ester linkages of fats to produce alcohols and fatty acids?
Lipases
High lipase along with decreased calcium is a
bad prognosis as it indicates that calcium was combined into Ca+ soaps due to high amount of liberated fatty acids.
(lipase method) Turbidimetric
Simpler and faster method. Lipase hydrolyzes fatty emulsion- decrease in absorbance. Stable substrates are difficult to find- often use triolein. Bilirubin falsely increases values.
Colorimetric
Coupled reactions with enzymes such as glycerol kinase peroxidase
Regan and Nagao is
an ALP that is a placental like fetal form which occurs in 3-15% of cancer patients.
Macro Ck is comprised of
CK-BB complexed with IgA and IgG
Mitochondrial Ck is bound to
Exterior surface of inner mitochondrial membranes of muscle brain and liver
What has to occur to see mitochondrial CK?
extensive tissue damage
RBCs are rich in
Adenylate kinase which reacts with ADP to produce ATP which participates in assay enzyme reaction, falsely elevating CK levels.
GGT is involved in
peptide and protein synthesis regulation of tissue glutathione levels transport of amino acids across cell membranes
GGT can be helpful differentiating
Source of elevated ALP, as GGT is normal in skeletal disorders and during pregnancy.
GGT is lower in females because
of the suppression of enzyme activity resulting from estrogenic or pregestational hormones.
Which enzyme has marked elevations for acute lymphoblastic leukemia
LDH
LDH forward reaction
Slower ; Lactate to pyruvate
LDH reverse reaction
Faster: pyruvate to lactate
LDH reactions referred to as
Wacker method
LDH isoenzyme’s structure includes:
M and H subunits with 4 chains
LDH 1 and LDH 2 are greatest in
Heart and RBCs
LDH 4 and LDH 5 are greatest in
Liver and skeletal muscle