What Is an Isoenzyme?

Isozymes (isozyme, isoenzyme) broadly refer to enzymes that catalyze the same reaction in organisms but have different molecular structures. According to the recommendations of the Biochemical Nomenclature Committee of the International Biochemical Union (IUB), only enzymes with multiple molecular structures due to different coding genes are called isozymes. The most typical isoenzyme is lactate dehydrogenase (LDH) isoenzyme. Isoenzyme genes are first transcribed into isoenzyme messenger ribonucleic acid, which is then translated to produce the peptide chains that make up the isoenzyme. Different peptide chains can exist as unpolymerized monomers or can be polymerized into pure polymers or Hybrids, thus forming different structural forms of the same enzyme. Isoenzymes are a group of enzymes that catalyze the same chemical reaction, but their protein molecular structure, physical and chemical properties, and immune properties are significantly different.

Isoenzyme

LDH isoenzymes were separated by electrophoresis, and their enzyme profiles were analyzed. It was found that there were five enzyme bands in each vertebrate tissue. Per enzyme

In animals and plants, the distribution and content of an enzyme's isoenzyme in various tissues and organs are different, forming a specific isoenzyme spectrum of each tissue, which is called tissue.

In biology, isozymes can be used to study species evolution, genetic variation, crossbreeding and individual development, and tissue differentiation. For example, the most primitive vertebrate lamprey (Lamprey) has only one type of LDH peptide chain, and evolved to higher-level fishes only have two types of peptide chains, A and B. Another example is to deduce the geographic origin of a species by censusing an isozyme spectrum among species with different geographical distribution. Animal and plant genetic variation can be identified by comparing isozyme profiles of offspring and parents. Forensic science can also use a variety of isozyme analysis to identify parent-child relationships. The presence of new varieties after cell or plant cross breeding can also be determined by comparison of isozyme profiles. In individual development, from the embryo

Isozyme map

From fetal birth to adulthood, with the differentiation and development of tissues, various isoenzymes also undergo a process of differentiation and transformation. A certain type of isozyme appears in most tissues of the embryo and becomes the main type, called the primitive isozyme. However, after birth, it gradually decreases in some tissues and is replaced by another type of isoenzyme, which is almost absent or minimal in embryonic tissues, and only exists in a few mature and differentiated tissues. Enzyme. At different developmental stages of plants, corresponding changes in isozyme patterns are also seen.

In medicine, isoenzymes are an important means to study the occurrence of cancerous tumors. The isoenzyme spectrum of cancerous tissues often undergo embryogenesis, that is, too many fetal isozymes are synthesized. If these changes can be reflected in the serum, changes in the serum isoenzyme spectrum can be used to diagnose cancer. Also. Because the isoenzyme spectrum is organ-specific, the measurement of serum isoenzymes can often more specifically reflect the pathological changes of a certain organ, such as the increase in serum LDH1 (B4) or MB type creatine kinase (CK-MB) Diagnosing myocardial infarction is a more specific indicator, and it is more reliable than measuring the total activity of serum LDH or creatine kinase (CK).