Discuss the use of enzymes in pharmaceutical diagnostic testing

Enzymes are of regular use in medicine and pharmaceutical engineering. They have several valuable industrial and medical applications and it is thought that it is through their ability to catalyse reactions and subsequently lowering the energy required for a reaction to occur which makes them of particular use in industry (Smith et al, 1997). Additionally, enzymes are able to be used in a variety of different ways which include their use in the manufacture of alcohol, washing detergents, not to mention their use in the pharmaceutical and diagnostic industry.
The use of enzymes in the pharmaceutical world is becoming increasingly common throughout medical research and practice. Biopharmaceutical companies, which specialize in the manufacture of disease-related biomolecules, are becoming increasingly reliant upon the use of enzymes in their work. This reliance is particularly evident within drug and biopharmaceutical companies which aim to develop therapeutics and diagnostics for the management of diseases such as cancer and arthritis.
Part of the reason for the success of the use of enzymes in the field of pharmaceutical drug testing is through their unique ability to target specific molecular sites within molecules and also to work at certain, often specific temperatures and under particular conditions unique to themselves. This provides scientists with an approach to target the precise regions of a molecular structure within particular directed conditions.
An example of a group of enzymes used in pharmaceuticals is the series of newly characterized enzymes known as kallikreins. These enzymes are a sub-group of the serine protease family, which were thought to have potential as cancer diagnostics and therapeutics for a long period of time after their discovery. After an investigation by
IBEX, a biopharmaceutical drug company however, it was found that the effects of kallikreins on tumour growth and behaviour using human ovarian cancer cell lines may not have been that which was initially described. It has since been confirmed that the kallikreins may present diagnostic or prognostic tools for certain cancers, and may even present therapeutic opportunities through their implications in promoting tumour growth or metastasis (King et al, 2007).
Perhaps most interestingly, the use of enzymes in pharmaceuticals offers an ability to generate new drug development data during research trials. From this research new drugs can be identified and subsequently new therapeutic strategies and alternatives functions found which were previously not associated with the functioning of particular enzymes. This phenomenon can be observed with the kallikreins, as the results in animal studies have suggested that instead of promoting tumour growth, several of the kallikreins may actually inhibit the growth or spread of tumours (King et al, 2007). Thus as a consequence of this information, it is thought that the kallikreins should no longer be considered just drug targets, at least in ovarian cancer, but should be regarded as presenting very good opportunities as therapeutic strategies for cancer treatment. 

In 2006 results from animal studies were presented at the American Association for Cancer Research in Washington, D.C. (King et al, 2007). This lead to the conduction of further additional animal tests to help decide if this drug candidate should be used in trials within humans. This is the method through which certain families of enzymes become used in diagnostic testing and get incorporated into large multinational diagnostic companies through their incorporation into high throughput clinical diagnostic machines (Crommelin and Sindelar, 2002).
In recent years, there has been a large focus on the use of enzymes in the search for cancer treatments and therapeutics. An example of such is the HAAH-based cancer serum test makes use of the enzyme human aspartyl (asparaginyl) Beta-hydroxylase (HAAH). (Keith et al, 2008) This test thought to become one of the most useful diagnostic tests for detection of the presence of a tumour within its early stages within multiple different organs (Keith et al, 2008). Furthermore, it is thought that through the use of diagnostic tests utilizing HAAH and other organ specific tumor markers (alongside imaging procedures), clinicians may be able to diagnose cancers in their curable stage.
The enzyme, HAAH, used in cancer assays is thought to be over-expressed in primary tumor tissue in eighteen different tumor types that have been tested. These tumor types include cancers of the pancreas, breast, ovary, liver, colon, prostate, lung, brain, and bile duct. Furthermore, HAAH over- expression has been detected in a large number of tumor specimens, a finding which has not been reciprocated in normal or adjacent, non-affected tissue (Keith et al, 2008).
Recent findings in preclinical studies have indicated that over-expression of HAAH is sufficient to induce cellular transformation, to increase cell motility and invasiveness, and to establish tumor formation in animals. When HAAH expression is reduced, a marked reduction in tumour progression has been observed and tumour cells have been seen to return to their ‘normal’ state. As it is the case that HAAH is over-expressed on the surface of cancer cells, it is possible that the expression of the enzyme could aid in the detection of cancer, in drug delivery mechanisms, and enzyme inhibition (Panacea Pharmaceuticals, 2004). Thus, the function of enzymes in identification of pathological processes is another method through which they may prove to be highly useful in the area of pharmaceuticals.
The field of pharmacogenetics, which has developed over the past fifty years, has further enhanced the application of enzymes in pharmaceutical drug testing. Research has identified genetic variations in the abilities of patients to metabolise drugs prescribed to them for certain conditions (Wolf et al, 2000). This is known as an individual’s “metabolizer phenotype” (Wolf et al, 2000) and is understood to have an effect on the patient’s ability to react to certain drug types. One example of an enzyme affecting drug metabolism is the P450 enzymes located in the liver (Crommelin and Sindelar 2002). These enzymes can be used to explain how some pharmacological agents are highly toxic for one individual yet have therapeutic advantages for another. Hence, it is important to have a clear understanding between the natural functioning of the enzymes of the human body and the drugs which they metabolise in order to develop pharmaceutical agents effectively.
As already inferred, the notion of pharmaceutical drug testing is important in the development of medical therapeutics used to identify deficiencies in certain physiological pathways which may be linked to particular medical conditions. An example of a physiological pathway which may involve the use of enzymes to detect its presence is the physiological pathway leading to the development of angioedema. It is thought that ACE or vasopeptidase inhibitor may be implicated in the development of the disease (Weber, 2002). Additionally, detection and/or measurement of dipeptidyl peptidase IV (DPP IV) enzyme activity and aminopeptidase P (APP) enzyme activity is considered to be a predictor of the risk of suffering from angioedema. This knowledge has lead to the development of therapeutic tests which identify the presence of these enzymes within patients thought to be at risk of the disease so that each individual patient may be treat with the necessary angiotensin-converting enzyme (ACE) inhibitor and/or a vasopeptidase inhibitor (combined ACE and neutral endopeptidase (NEP) inhibitor), both of which are therapeutic enzymes commonly used the treatment of hypertension (high blood pressure), diabetes, and cardiac and renal diseases.
Screening for diabetes is also commonly carried out through the use of enzymes. Testing of a patient’s blood sugar concentration usually requires the use of two enzymes: glucose oxidase and hexokinase as these enzymes are known to catalyse the conversion of glucose (found in the urine of a patient with diabetes, due to an imbalance of the homeostatic mechanisms found within the body) into another chemical compound, inducing a colour change in urine solution. This diagnostic test is perhaps one of the oldest pharmaceutical methods making use of enzymes, and is still used today (Bernard, 2001).
The test highlights the importance of an enzymes ability to identify one particular substrate within a mixed solution in the diagnosis of a clinical disease phenotype.