Lipid apoenzymes

Enzymes are proteins with catalytic properties. The catalytic properties are quite specific, which makes enzymes useful in analytical studies. Some enzymes consist only of protein, but most enzymes contain additional nonprotein components such as carbohydrates, lipids, metals, phosphates, or some other organic moiety. The complete enzyme is called holoenzyme the protein part, apoenzyme and the nonprotein part, cofactor. The compound that is being converted in an enzymic reaction is called substrate. In an enzyme reaction, the substrate combines with the holoenzyme and is released in a modified form, as indicated in Figure 10-1. An enzyme reaction, therefore, involves the following equations ... 

Little is to be gained by listing further instances in which these various compounds can be interchanged because the interactions between vitamin E, coenzyme Q, and selenium are still unknown [130-135]. There are two major theories the first proposes that all these compounds function in metabolism as antioxidants, protecting, for example, the integrity of the lipid membrane the second holds that these compounds react with certain apoenzymes in specific but still unknown metabolic reactions. 

Similar results are obtained when the supernatants are titrated with other lecithins, indicating that the apoenzyme released from diabetic mitochondria is not defective with respect to lipid binding capacity. This results also is a proof that the apoenzymes obtained from normal or diabetic rat liver mitochondria are functionally (and, consequently, structurally) identical. 

---