Preferred provider organization
In health insurance in the United States, a preferred provider organization (PPO), sometimes referred to as a participating provider organization or preferred provider option, is a managed care organization of medical doctors, hospitals, and other health care providers who have agreed with an insurer or a third-party administrator to provide health care at reduced rates to the insurer's or administrator's clients.
Polyphenol oxidase
Tyrosine is a key compound of pigmentation/browning reaction through the action of polyphenol oxidase. Discrimination of this pigmentation reaction is responsible for various types of diseases and disorders.There are two types of inhibitor of PPO, those competitive to oxygen in the copper site of the enzyme and those competitive to phenolics. Tentoxin has also been used in recent research to eliminate the PPO activity from seedlings of higher plants. Tropolone is a grape polyphenol oxidase inhibitor. Another inhibitor of this enzyme is potassium pyrosulphite (KSO). Banana root PPO is strongly inhibited by dithiothreitol and sodium metabisulfite. Endogenous proteinous fractions act endogenous inhibitor/regulator of onion leaves PPO (monophenol monooxygenase and o-diphenol oxidase) Potassium dithionite (or potassium hydrosulfite) is also an inhibitor of PPO.