A cysteine is added to 4′-phosphopantothenate by the enzyme phosphopantothenoylcysteine synthetase to form 4-phospho-N-pantothenoylcysteine (PPC). This step is coupled with ATP hydrolysis. PPC is decarboxylated to 4′-phosphopantetheine by phosphopantothenoylcysteine decarboxylase
4′-Phosphopantetheine is adenylated (or more properly, AMPylated) to form dephospho-CoA by the enzyme phosphopantetheine adenylyl transferase
Finally, dephospho-CoA is phosphorylated to coenzyme A by the enzyme dephosphocoenzyme A kinase. This final step also requires ATP.This pathway is suppressed by end-product inhibition, meaning that CoA is a competitive inhibitor of pantothenate kinase, the enzyme responsible for the first step.Coenzyme A is necessary in the reaction mechanism of the citric acid cycle. This process is the bodys primary catabolic pathway and is essential in breaking down the building blocks of the cell such as carbohydrates, amino acids and lipids, for fuel. CoA is important in energy metabolism for pyruvate to enter the tricarboxylic acid cycle (TCA cycle) as acetyl-CoA, and for α-ketoglutarate to be transformed to succinyl-CoA in the cycle. CoA is also required for acylation and acetylation, which, for example, are involved in signal transduction, and various enzyme functions. In addition to functioning as CoA, this compound can act as an acyl group carrier to form acetyl-CoA and other related compounds; this is a way to transport carbon atoms within the cell. CoA is also required in the formation of acyl carrier protein (ACP), which is required for fatty acid synthesis. Its synthesis also connects with other vitamins such as thiamin and folic acid.
Vinorelbine (NVB), sold under the brand name Navelbine among others, is a chemotherapy medication used to treat a number of types of cancer. This includes breast cancer and non-small cell lung cancer. It is given by injection into a vein or by mouth.Common side effects include bone marrow suppression, pain at the site of injection, vomiting, feeling tired, numbness, and diarrhea. Other serious side effects include shortness of breath. Use during pregnancy may harm the baby. Vinorelbine is in the vinca alkaloid family of medications. It is believed to work by disrupting the normal function of microtubules and thereby stopping cell division.Vinorelbine was approved for medical use in the United States in 1994. It is on the World Health Organizations List of Essential Medicines. Medical uses
Vinorelbine is approved for the treatment of non-small-cell lung cancer. It is used off-label for other cancers such as metastatic breast cancer. It is also active in rhabdomyosarcoma. Side effects
Vinorelbine has a number of side-effects that can limit its use:
Chemotherapy-induced peripheral neuropathy (a progressive, enduring and often irreversible tingling numbness, intense pain, and hypersensitivity to cold, beginning in the hands and feet and sometimes involving the arms and legs), lowered resistance to infection, bruising or bleeding, anaemia, constipation, vomitings, diarrhea, nausea, tiredness and a general feeling of weakness (asthenia), inflammation of the vein into which it was injected  (phlebitis). Seldom severe hyponatremia is seen. Less common effects are hair loss and allergic reaction. Pharmacology
The antitumor activity is due to inhibition of mitosis through interaction with tubulin.