Therapeutic Enzymes Flashcards
What is the function of asparaginase?
It’s an enzyme that catalyzes the hydrolysis of L-asparagine, producing aspartic acid and ammonia.
How was the effectiveness of asparaginase discovered?
- In the late 1970s
- Serum from healthy guinea pigs transferred into mice with leukemia inhibited the proliferation of leukemia cells.
- The active agent was asparaginase.
Why is asparaginase used in treating certain forms of human leukemia?
Many transformed cells, including leukemia cells, lose the ability to synthesize asparagine.
Asparaginase:
- deprives these cells of asparagine
- by hydrolyzing plasma asparagine
- making it an effective treatment for leukemia.
What is an example of a specific form of asparaginase used in the treatment of childhood acute lymphoblastic leukemia?
PEG-L-asparaginase
Has been approved for the treatment of refractory childhood acute lymphoblastic leukemia.
What is the importance of high substrate affinity in therapeutically useful asparaginases?
- The plasma concentration of asparagine is typically low,
- Therapeutically useful asparaginases must have a high substrate affinity
- To effectively deplete asparagine in the body.
Which organisms have been studied extensively for their asparaginase activity?
- E. coli
- Erwinia
- Pseudomonas
- Acinetobacter
shown to be effective in inhibiting the growth of various leukemias and other transformed cell lines.
What are some common side effects associated with asparaginase treatment?
- severe nausea
- vomiting
- diarrhea,
- compromised liver and kidney function
due to transient asparaginase deficiency in various tissues.
Why is the lung tissue in cystic fibrosis patients susceptible to frequent and recurrent microbial infections?
- Due to the pathophysiological changes induced in the cystic fibrosis lung
- Particularly by Pseudomonas species.
What happens as a result of the presence of microbes in the lung?
- Phagocytic neutrophils digest microbes in the cystic fibrosis lung
- They release large quantities of DNA,
- Significantly increases the viscosity of the respiratory mucus.
Why is it beneficial to break down DNA and reduce the viscosity of respiratory mucus in cystic fibrosis?
Breaking down DNA and reducing the viscosity of respiratory mucus in cystic fibrosis has obvious clinical benefits as
* it helps in improving airway clearance
* reducing the risk of respiratory complications.
What experiments were undertaken for the treatment of cystic fibrosis?
Since 1950s
Experiments entailing inhalation of DNase-enriched extracts of bovine pancreas
What were the issues associated with early experiments for cystic fibrosis treatment?
Raised concerns about:
Product safety
- Damage to underlying lung tissue by trypsin and other contaminants
Efficacy issues
- Due to neutralization of bovine DNase by the host immune system.
What was the solution to the safety and efficacy issues with DNase treatment for cystic fibrosis?
- Highly purified recombinant human DNase (rhDNase) has been used since the end of 1993
- It proved safe and effective
- Leading to marketing authorization under the tradename Pulmozyme.
How is Pulmozyme administered for cystic fibrosis treatment?
- Produced by an engineered CHO cell line
- Administered directly into the lungs by inhalation of an aerosol mist
- Generated by a compressed-air-based nebulizer system.
What did in vitro studies show regarding the use of rhDNase in cystic fibrosis treatment?
- That incubation of the rhDNase enzyme with sputum derived from a cystic fibrosis patient resulted in a significant reduction in sputum viscosity
- indicating its potential efficacy in improving airway clearance.
What is the approved use of α-galactosidase?
Approved for long-term enzyme replacement therapy in patients with Fabry disease
What is Fabry disease?
a genetic disease of lipid metabolism characterized by little or no liposomal α-galactosidase activity.
How does Fabry disease affect patients?
Affects patients by causing complex clinical manifestations that impact the nervous system, vascular endothelial cells, and major organs.
What is the consequence for untreated sufferers of Fabry disease?
Untreated sufferers of Fabry disease typically have a reduced life expectancy and usually die in their 40s or 50s
What are the names of the two recombinant α-galactosidases available on the market?
Fabrazyme - produced by Genzyme,
Replagal - produced by TKT Europe.
What are the reactive molecules generated by the incomplete reduction of oxygen?
- superoxide radical (O2-)
- hydrogen peroxide (H2O2)
- hydroxyl radical (OH-)
How do the superoxide and hydroxyl radicals impact cellular components?
Are highly reactive and can attack:
- membrane components
- Nucleic acids
- Other cellular macromolecules
leading to their destruction or modification.
What are some examples of pathological conditions associated with increased generation of superoxide or reduced levels of superoxide dismutase (SOD)?
Increased generation of superoxide (O2-) or reduced SOD levels have been implicated in various pathological conditions, including:
aging,
asthma,
accelerated tumor growth,
neurodegenerative diseases
inflammatory tissue necrosis.
What are the catalytic reactions catalyzed by SOD and catalase or glutathione peroxidase (GSH-px)?
SOD catalyzes the reaction:
O2- + O2- + 2H+ -> H2O2 + O2
catalase or GSH-px catalyzes the reaction:
H2O2 + H2O2 -> 2H2O + O2.
How has SOD been used medically?
SOD isolated from bovine liver or erythrocytes has been used as an anti-inflammatory agent in medical applications.
What is being evaluated regarding human SOD in relation to tissue damage prevention?
Human SOD expressed in recombinant systems is currently being evaluated to assess its ability to prevent tissue damage induced by exposure to excessively oxygen-rich blood.
What is debridement?
The process of cleaning a wound by removing foreign material and dead tissue.
Why is debridement necessary for wound healing?
Formation of a clot and scab on a wound surface can trap bacteria, leading to the multiplication of bacteria and slowed healing. Debridement helps remove bacteria and promote the healing process.
How can debridement be achieved?
Through physical means, such as cutting away dead tissue and cleaning the wound, or by using proteolytic enzymes to facilitate the process.
What are some common microbial enzymes used as debriding agents?
- collagenase (in Collagenase Santyl ointment)
- papain (in Gladase-C ointment)
- trypsin (in Granulex V spray)
How is collagenase obtained for therapeutic use?
Collagenase used therapeutically is usually obtained from cell fermentation supernatants of Clostridium histolyticum, although it can also be produced by animal cell culture.
Where is papain derived from for its use as a debriding agent?
Papain, a cysteine protease, is isolated from the latex of the immature fruit and leaves of the plant Carica papaya.
How is trypsin obtained for medical use as a debriding agent?
- By enzymatic activation of trypsinogen,
- Extracted from the pancreatic tissue of slaughterhouse animals.
Besides enzyme-based debridement, what other method has been historically used to clean wounds?
- By the application of protease-containing maggot saliva
- The use of maggots themselves directly onto wound tissue.
