Plasma proteins

Substrate concentration 

• Increase rxn speeds = more likely to bind

• Michaelis-Menten equation

Michaelis-Menten curve

• Maximum velocity = Vmax

  • when substrate concentration is high enough that all enzyme molecules are bound to the substrate and all active sites are engaged

• Measure velocity = V

• Substrate concentration = [S]

• Constant of enzyme for specific substrate = Km

Michaelis-Menten equation

V = Vmax [S] / Km + [S]

Zero-order kinetics

• Reaction rate depends only upon enzyme concentration

• When all enzymes are saturated with substrate

• substrate in excess

First order kinetics

• Reaction rate is directly proportional to substrate concentration

• Enzyme in excess

Lineweaver-Burk plot

• a double-reciprocal graph of an enzyme's Michaelis-Menten kinetics

• Allows Km and Vax to be determined

Competitive inhibition

• Binds directly to the active site of an enzyme

• Can be overcome if conc. of the substrate is higher than inhibitor

• Km is increased Vmax is unaltered

Noncompetitive inhibition

• inhibitor binds to sites other than the active site (allosteric site)

• cannot be reversed by substrate or overcome

• Km is unchanged and Vmax is decreased

Uncompetitive inhibition

• inhibitors bind to the enzyme substrate complex

• Prevent product from being formed

• Increasing substrate increases inhibition = more complexes formed

• Km and Vmax are decreased

NAD+/NADH

• coenzyme NAD+ major electron acceptor

• NADH absorbs light at 340nm

• NAD+ does not absorb light 340nm

• Change in conc. correlated with NADH

Creatine Kinase

• CK shows highest activity in various parts

• 3 isoenzymes

  • CK - 1-->3

• Ck levels are increased in acute MI and muscular dystrophy

• 25 - 170 U/L

• Macro CK in elderly women

• Mitochondrial CK - pt with advanced malignancy

CK-1 CKBB

found in brain and intestines

CK-2 CKMB

found mostly cardiac muscle

CK-3 CKMM

found in skeletal and cardiac muscle

Lactate dehydrogenase LD

• LD1 migrates fastest to anode

• LD5 migrates slowest

• LD2 > LD1 = healthy

• total LD nonspecific marker for tissue injury and proliferation

• 100 - 225 U/L

Lactate dehydrogenase LD isoenzymes

1. LD1 = migrates fastest

2. LD2 = Decrease will cause LD1/D2 flip

3. LD3 = pulmonary disease and carcinoma

4. LD4 = help cells produce energy from sugar

5. LD5 = Liver and skeletal muscle

6. LD6 = severe shock, acidosis, sepsis

AST enzyme

• aspartate aminotransferase

• Viral hepatitis 100x

• Cirrhosis 4x

• Skeletal muscle disorders 4-8x

• pulomnary embolism

ALT enzyme

• Hepatocellular injury

• Obstructive hepatic disorders

• higher AST in acute liver disorders

ALP enzyme

• 6x conc. of RBCs

• Liver biliary tract obstruction 3-10x

• Bone elevated with osteoblast involvement

• Highest in Page's disease

• Pregnancy

• Decreased in hypophosphatasia

ACP enzyme

• Prostate cancer

• Forensic rape investigation

• Body decomposition

GGT enzyme

• Most sensitive for liver

• Chronic alcoholism 2-3x

• differentiate reason for elevated ALP

• GGT is normal in skeletal growth and pregnancy

Protein breakdown

• Protein breakdown --> urea and NH4

• Synthesized in the liver and secreted by hepatocyte into circulation

• immunoglobulins synthesized by plasma cells

Albumin enzymes

Osmotic force - distribution of water throughout body

Protein balance and nitrogen balance

Rate of protein anabolism (synthesis) = the rate of protein catabolism exceeds protein anabolism

Negative N2 balance

protein catabolism exceeds protein anabolism (formation)

Positive N2 balance

protein anabolism is occuring at a faster rate than protein catabolism

Isoeletric point

• pH at which an amino acid or protein has no net charge

• pH greater than pI = protein becomes negatively charged

• pH less than pI = protein becomes positively charged