Is sinemet an maoi drug

No. Sinemet is a combination of a prodrug (levodopa, which is converted in the body to dopamine) and an inhibitor that prevents the conversion (the enzyme it inhibits is DOPA decarboxylase; MAOI drugs inhibit monoamine oxidase). The inhibitor is highly polar and cannot pass the blood-brain barrier, so it inhibits the conversion of levodopa to dopamine in the body generally, but allows conversion within the brain. This is done because high levels of dopamine outside the brain can result in nausea and vomiting.