CC2 RODRIGUEZ

• Enzymes


  Proteins in nature produced by living cells that hasten chemical reactions in organic matter
• Enzymes


  • They are large molecules that are normally confined within cells unless increased membrane permeability allows them to enter the blood
  • They frequently appear in the serum after cellular injury, degradation of cells or from storage areas
  • They are measured in terms of their activity and not in terms of their absolute values
  • Abnormal large amounts of enzymes in serum are used clinically as evidence of organ damage
  • Each enzyme catalyzes a single reaction or limited number of chemical reactions and is specific for substrate that it converts to a defined product
  • The tissue and cellular locations of enzymes are crucial in the diagnosis and management of organ dysfunctions and diseases
• Causes of Elevated Plasma Enzyme Levels

  • Tissue necrosis and degeneration (death of enzyme-containing cells)
  • Impaired removal of enzyme from plasma
  • Normal cell turnover
  • Increased permeability of cell membrane
  • Increase in the production of enzymes by cells
  • Decreased clearance of enzymes from the circulation
• An enzyme accelerates the rate of reaction, reducing the time required to reach equilibrium
• A constant change in absorbance per unit time occurs only when the rate of the reaction is zero-order
• An enzyme does not alter the free energy or direction of a reaction, but it alters the energy of activation by forming a metastable intermediate, the ES complex
• Most enzymes are measured by monitoring the rate of absorbance change (kinetic assay) at 340 nm as NADH is reduced or consumed, and it allows direct reporting either by IU or KU
• In first-order reaction, the enzymes are used as reagents to measure a specific analyte
• Kinetic methods are more accurate and can easily identify any change in the reaction and samples requiring treatment (dilution)
• In non-kinetic assay, absorbance is made at 10-second intervals for 100 seconds
• Endpoint measurement determines the concentration of substrate or product at a specific time after addition of the sample (bedside glucose testing using strips)
• Enzyme activity measurements may not be accurate if enzyme inhibitors are present, essential cofactors are not included in the assay, and when there is improper sample storage
• The Lineweaver-Burk plot is an illustration of the reciprocal of the substrate concentration (x-axis, 1/S) and the reciprocal of the reaction velocity (y-axis, 1/V), in which both are components of the enzyme kinetics
• Alkaline Phosphatase (ALP)


  Alkaline Orthophosphoric Monoestr Phosphohydrolae
• Alkaline Phosphatase (ALP)


  • It is a non-specific enzyme capable of reacting with many different substrates
  • It functions to liberate inorganic phosphate from an organic phosphate ester with the concomitant production of an alcohol
  • It is predominantly found in the cell membranes
• Major tissue sources of Alkaline Phosphatase (ALP)

  • Liver
  • Bone
  • Placenta
  • Intestinal
• Reference range for Alkaline Phosphatase (ALP)

  30-90 U/L
• Major Isoenzymes of Alkaline Phosphatase (ALP)

  • Liver ALP
  • Bone ALP
  • Placental ALP
  • Intestinal ALP
• The most abundant plasma alkaline phosphatase (ALP) isoforms are 1, producing liver, bone, and kidney isoenzymes
• Genes on chromosome 2 code for placental and intestinal ALPs
• Bone isoenzyme of Alkaline Phosphatase (ALP)


  Increases due to osteoblastic activity and is normally elevated in children during periods of growth and in adults older than age 50 years (geriatric)
• During period of growth and muscle development, serum ALP and creatinine levels increase
• In normal pregnancy, increased ALP activity can be detected between 16 and 20 weeks of pregnancy
• Presence of intestinal ALP

  Depends on the blood group (secretor gene and H substance) of the individual; B isoenzyme in serum is higher in individuals of groups B and O than in A and AB individuals because of differences in intestinal ALP levels
• Placental ALP


  Is lower in pregnant women of blood groups A and AB
• Carcinoplacental ALP


  • Regan ALP
  • Nagao ALP
• Regan ALP


  • It is found in lung, breast, ovarian, and gynecological cancers
  • It is the most heat-stable ALP (65' C for 30 minutes)
  • It is inhibited by phenylalanine reagent, a bone ALP co-migrator
  • It is coded by the gene on chromosome 2
• Nagao ALP


  • It is found in adenocarcinoma of the pancreas and bile duct, and in pleural cancer
  • It is a variant of Regan ALP
  • It is inhibited by L-leucine and phenylalanine
• When total ALP levels are increased, it is the major liver fraction that is most frequently elevated, especially in obstructive jaundice
• ALP is increased in obstructive jaundice due to greater rate of secretion
• In biliary tract obstruction, serum ALP increases are primarily a result of increased synthesis of the enzyme by induced cholestasis
• When there is obstruction in the flow of conjugated bilirubin into the canaliculus, it is accompanied by elevated plasma B2, ALP, and gamma-glutamyltransferase (GGT)
• For bone disorders, highest elevations occur in Paget's disease (osteitis deformans)
• In other bone disorders where there are active osteoblasts, such as in osteosarcoma, tumor metastatic to bone, and metabolic bone disease, serum ALP is also increased
• Bone ALP isoform known as B1x is detected in the serum of dialysis patients
• B1x isoform is used to study low bone mineral disease (BMD) in patients with chronic kidney disease
• B1x isoform is also increased in the serum of individuals with BMD of the hip, which is composed mainly of trabecular bone
• Serum ALP is elevated in cases of abortion, and may be increased when there is difficulty during pregnancy and birthing
• Transient low serum ALP may occur after blood transfusion or cardiopulmonary bypass
• Prolonged low levels of ALP occur in hypophosphatasia