Question

A student, learning that someone has an elevated blood level of lactate dehydrogenase (LDH), wonders how the enzyme got into this person's blood and worries about whether it will digest the blood. What explanation can you give to allay the student's fears?

Short answer

LDH is an enzyme found in almost every cell of our body and plays a role in energy production. Elevated blood levels of LDH occur due to tissue damage or injury, rather than being a direct cause of harm. It is a metabolic enzyme, not a digestive one, so it doesn't have the ability to digest or break down blood components. Therefore, the student shouldn't worry about LDH digesting the blood, but elevated levels may indicate the need for further medical investigations to diagnose the specific cause and provide appropriate treatment.

Step-by-step solution

Understand what Lactate Dehydrogenase (LDH) is

Lactate Dehydrogenase (LDH) is an enzyme found in almost every cell of the body. It is responsible for the conversion of lactate to pyruvate and pyruvate to lactate, through a process known as anaerobic glycolysis, when there is insufficient oxygen supply. This provides energy for cells when oxygen is not available. So, its primary function is participating in energy-producing metabolic processes.

How LDH is present in the blood

Due to the ubiquitous nature of LDH, it is found in many tissues of the body including the heart, liver, kidneys, muscles, and lungs. When any of these tissues or cells are damaged, LDH leaks from the injured cells into the bloodstream. Elevated blood levels of LDH are an indication of tissue damage or injury, rather than a direct cause of harm.

Why LDH doesn't digest the blood

LDH is a metabolic enzyme that plays a role in producing energy for cells; it is not a digestive enzyme. Furthermore, our blood consists of cells (red and white blood cells), proteins, and other dissolved substances, which form a complex and tightly regulated system. These components maintain the proper functioning of the circulatory system and blood vessels. LDH does not have the ability to break down or digest these components, so it doesn't pose any risk to the blood.

Reassuring the student

In summary, LDH is present in the blood due to tissue damage or injury, where the enzyme has leaked out of the affected cells. Its role is to assist in energy production, and not to digest or break down blood components. Thus, the student should not worry about LDH digesting the blood. Elevated blood levels of LDH can be a sign of underlying tissue damage or disease, and further medical investigations may be required to diagnose the specific cause and provide appropriate treatment.

Key concepts

Anaerobic Glycolysis

Anaerobic glycolysis is a critical metabolic pathway that allows cells to produce energy when oxygen levels are low. This process plays a vital role particularly in our muscles during intense exercise, where oxygen supply may not meet the demand. In essence, it allows cells to convert glucose into lactic acid and generate small amounts of energy in the form of ATP (adenosine triphosphate).
During this process, lactate dehydrogenase (LDH) is the enzyme that catalyzes the final step, ensuring the conversion of pyruvate to lactate when oxygen is scarce, and vice versa when oxygen becomes available. This reversible reaction is crucial in maintaining the balance of NADH/NAD+ required for glycolysis to continue. Hence, elevated levels of LDH in the blood could indicate that the body has been relying heavily on anaerobic pathways due to hypoxic conditions or tissue damage causing cells to burst and release their content, including LDH, into the bloodstream.

Enzyme Function in Metabolism

Enzymes like lactate dehydrogenase (LDH) act as biological catalysts that speed up chemical reactions in the metabolism without being consumed in the process. Each enzyme works on a specific substance, known as a substrate; in the case of LDH, its substrates are lactate and pyruvate. Enzyme function is indispensable to metabolism as they facilitate the reactions necessary for life, from breaking down nutrients for energy to synthesizing the components cells need to function.
In the absence of these enzymes, reactions would occur too slowly to sustain life. LDH in particular is involved in anaerobic glycolysis where it helps a cell produce energy when oxygen is limited. Enzymes also play a role in the regulation of metabolic pathways, which can be seen as a complex network of interdependent reactions, ensuring that the body's energy needs are met efficiently and in response to varying conditions.

Blood Biomarkers of Tissue Damage

Blood biomarkers like LDH are substances that can be measured in the blood and provide information about the health status of an individual. LDH levels become elevated in the blood when there is tissue damage because it is released from damaged or destroyed cells. Therefore, it serves as an indicator that some form of cellular injury has occurred.
Several conditions can lead to an increase in LDH levels, including myocardial infarction (heart attack), hemolysis (destruction of red blood cells), hepatitis (liver inflammation), and certain types of cancers. The measurement of LDH and other enzymes are commonly used in clinical settings to help diagnose, monitor, and manage diseases. Because there are several types of LDH that are more concentrated in specific tissues, the patterns of LDH isoenzymes in the blood can sometimes help pinpoint the location of tissue damage. However, it's important to note that while elevated LDH levels indicate tissue damage, they don't reveal the cause of the damage, necessitating further medical investigation.