Enzymes Information and Courses from MediaLab, Inc.

Prompt testing (within one hour of collection of the urine sample) or refrigeration of the specimen is necessary because the glycolytic enzymes from the cells and bacteria, if present, will decrease the sugar in the urine.

HIV consists of nine genes. Three of the genes provide genetic information for the capsid proteins, envelope proteins, and viral enzymes. The other six genes are regulatory genes, controlling functions such as uncoating of the HIV genome and the penetration of host cells. Gene Number Abbreviation Gene Function 1 gag capsid proteins 2 pol viral enzymes 3 env envelope proteins 4 vif regulatory gene 5 tat regulatory gene 6 vpu regulatory gene 7 nef regulatory gene 8 vpr regulatory gene 9 rev regulatory gene

At this time an enzyme called protease, using enzymes and proteins from preliminary protein molecules, forms capsomere segments which unite to form an icosahedral capsid.The capsid then changes into a bullet-shaped capsid and surrounds the viral RNA.Next some of the host cell's membrane joins with the viral glycoproteins gp120 and gp41 to form the spikes.Last, part of the host cell's surface membrane encloses the virus and becomes the envelope.

After penetration of the cell membrane by the gp41, the HIV capsid enters the cell's cytoplasm. Next, cellular enzymes strip away the capsid so that the HIV genome is released. Also stripped away are proteins p24 and p17. Protein 24 coats the HIV genome and protein 17 lines the inside of the capsid.

Once the capsid and p24 and p17 have been stripped away, an enzyme complex known as reverse transcriptase is released.One of the enzymes in this complex is DNA polymerase. It synthesizes a single-stranded DNA copy using one of the HIV-RNA molecules as a template.Another enzyme in this complex, called ribonuclease, then destroys the original RNA molecules while the DNA polymerase synthesizes another single-stranded DNA molecule, this time using the first DNA copy as the template.The result is a double-stranded DNA molecule.

Specialists in immunohematology perform all testing prior to blood transfusions and work to prevent transfusion infections. They also investigate any post-transfusion reactions. This specialty includes all lab procedures performed in the specialty of histocompatibility. Specialists in clinical chemistry analyze body fluids such as blood, urine, and spinal fluid to determine the chemical makeup, including the amount of carbohydrates, proteins, enzymes, and trace elements. The special covers urine microscopics and chemical evaluation of the liver, kidneys, lungs, heart, and other vital organ systems. This specialty also covers all testing performed in the specialties of radioassay and blood gas analysis. Specialists in blood banking can perform all immunohematology testing as well as testing from the specialties of clinical chemistry, hematology and serology/immunology that relates to donor blood. Specialists in immunohematology, clinical chemistry, hematology, and serology / immunology may perform all tests in the blood banking specialty.

Antibody - A modified type of serum globulin synthesized by lymphoid tissue in response to antigenic stimulus. By virtue of specific combining sites each antibody reacts with only one antigen. Anucleate - Having no nucleus. Azurophilic granules - The well-defined large reddish granules (lysosomes) which may be present in large lymphocytes. They are called "azurophilic granules" because they stain blue with the azure stains which were originally used. Basophilic granules - Specific granules present in the cytoplasm of basophils. These granules are large and stain purple-black due to their strong affinity for basic stain. B-cell - Bone marrow derived lymphocytes which produce humoral antibodies. Biconcave - Having two concave surfaces. Cellular Immunity - The capacity of a small proportion of lymphoid population to exhibit response to a specific antigen. Chromomere - The centrally located granular portion of the platelet. Clone - A population of cells descended from a single cell. Delayed Hypersensitivity - (part of cellular immunity) that develops slowly over a period of 24-72 hours after an antigenic stimulus. It consists of an accumulation of cells around small vessels and/or nerves. Example: Tuberculin skin test reaction. Digestive Enzyme - A substance that catalyzes or accelerates the process of digestion. Eosinophilic Granules - Specific granules present in the cytoplasm of eosinophils. These granules are large, refractile spheres which stain reddish-orange due to their strong affinity for acid stain. Erythrocyte (red blood cell, RBC) - One of the elements found in peripheral blood. Normally the mature form is a non-nucleated, circular, biconcave disk adapted to transport respiratory gases. Fixed Macrophage - A phagocyte that is non-motile. Free Macrophage - An ameboid phagocyte present at the site of inflammation. Graft Rejection - A transplanted tissue that is rejected by the body's antibodies. Graft vs. Host Reaction - A complication that occurs when an implanted piece of tissue, which contains antibodies, rejects the host's tissue. Granulocyte - A leukocyte which contains granules in its cytoplasm, i.e., neutrophilic, eosinophilic, or basophilic granules. Half-life - is the length of time it takes for half of the cells circulating at a given time to leave the blood for the tissues. Hemocyte - Any blood cell or formed element of the blood. Hemostasis - A mechanism of the vascular system to arrest an escape of blood. It involves an interaction between blood vessels, platelets, and coagulation. Heparin - A mucopolysaccharide acid which, when present in sufficient amounts, functions as an anticoagulant by inhibiting thrombin. Histamine - A powerful dilator of capillaries and a stimulator of gastric secretions. Humoral Immunity - Acquired immunity produced after response to an antigenic stimulus in which B cells produce circulating antibodies. Hyalomere - the clear, blue non-granular zone surrounding the chromomere of a platelet. Immune Response - The interaction of a cell and an antigen that results in a proliferation of the cell and a capacity to produce antibodies. Isotonic Fluid - A fluid whose elements have an equal osmotic pressure. Leukocyte (white blood cell, WBC) - One of the formed elements of the blood; involved primarily with the body's defense. Lysosome - A microscopic body within cell cytoplasm; contains various enzymes, mainly hydrolytic, which are released upon injury to the cell. Megakaryocyte - A giant cell of the bone marrow from which platelets are derived. Mononuclear - A cell having a single nucleus.

When a neutrophil is faced with a microorganism or foreign particle, phagocytosis begins. The neutrophil extends pseudopods around the foreign material and engulfs it. Digestive enzymes present in the neutrophilic granules are released into the vacuole containing the foreign particle, and the particle is destroyed. In most cases a mild infection enhances the function of neutrophils while a severe infection impairs their function.

In addition to protein availability, other factors may affect drug absorption and distribution in the body as a whole or at specific sites within the body. The following table highlights some of these other factors. Factor Discussion Regional blood flow Reduced area blood flow can be seen in diabetics and enhanced blood flow can be seen in tumors. Lipid solubility of the drug The more lipophilic a drug is, the more likely it will enter the central nervous system. The integrity of the GI tract In a diseased gut, an orally-administered drug may not be absorbed as expected. Age Drug kinetics and dispositions change throughout life. In general, metabolism of drugs is reduced in the elderly. Genetics Mutations or deletions in drug metabolizing enzymes can greatly affect a drug's disposition.

However, every patient is unique. Changes in the gut (if the drug is taken orally), genetic variations in the liver's metabolizing enzymes, and the status of organs (like the kidneys and liver) all affect how a drug will be handled by an individual. TDM helps to ensure that a dosing regimen is appropriate for a given patient.

It has been said that we live in a new era of "individualized medicine". One of the primary drivers for this idea is the emerging field of pharmacogenomics (PGx). Pharmacogenomics (PGx) is the study of how individual variations in the human genome affect responses to medications. The term "pharmacogenetics" is also used for this discipline (people in the field use both terms); however, the term 'pharmacogenomics' is becoming more popular since we now know the entire human genome. The primary reason that individuals metabolize and respond to drugs differently is the inter-individual differences in receptor proteins and enzymes that metabolize the drugs. Mutations in these receptor proteins and enzymes can give rise to very different responses to drugs. In PGx, these mutations are referred to as variants.

Many CYP450 enzymes have been characterized, and the substrates (drugs) that each can recognize have been worked out to a large extent. These subfamilies of CYP450 enzymes have all been associated with polymorphisms that can affect drug disposition: CYP1A2, CYP2C9, CYP2C19 and CYP2D6.

Variables other than mutations also affect CYP450 enzymes. Many drugs are able to induce CYP450 enzymes, and CYP450s can be inhibited by a variety of substances. For example, CYP2D6 can be inhibited by the common medications cimetidine (Tagamet) and fluoxetine (Prozac). Since many patients are on multiple medications and since dietary and environmental factors can change, CYP450 expression levels cannot be solely predicted based on their genotype. Some CYP450 inducers and inhibitors are listed in the table on the following page.

By knowing a patient's disposition to specific drugs, the physician should be able to start the patient on an appropriate regimen rather than perfecting treatment based on trial and error. Drugs whose metabolism may prove to be problematic can be avoided, and second-line therapies that are metabolized by different, unaffected enzymes can be chosen. Clinical chemists, pharmacologists, and physicians need to translate knowledge of CYP450 polymorphisms into clinically-validated treatment algorithms. Dosing recommendations for PM, EM, IM and UM patients are beginning to appear in the literature for various classes of drugs, and the FDA is encouraging the incorporation of pharmacogenomic testing in the development process for new drugs.

Semen is produced as a combination of secretions from the different regions of the male reproductive tract. Each fraction differs in chemical composition and function. The combination of these fractions during ejaculation results in the optimal environment for transporting sperm to the endocervical mucus in the female. Spermatozoa are produced in the testes. They mature in the epididymis. The testes also produce testosterone and inhibin.Fluid from the seminal vesicles accounts for approximately 70% of semen volume. The seminal vesicles are the source of fructose in semen. Fructose is used by the spermatozoa as an energy source.The prostate gland supplies about 20% of the volume of semen. Its fluids include acid phosphatase and proteolytic enzymes that lead to coagulation and subsequent liquefaction of semen. The prostate also contains most of the IgA found in semen.The bulbourethral gland produces mucoproteins that make up about 5% of the volume of semen.