The Wraith enzyme is a component of the Wraith feeding process. When a Wraith feeds on a human, the process is so traumatic that under ordinary circumstances the human would die almost immediately. To counteract this, the Wraith injects an enzyme into the human which strengthens the body while draining away their life, allowing the Wraith to gain the maximum amount of sustenance possible. If the feeding process is interrupted, the Wraith may reflexively inject their victim with an overdose of the enzyme.
By itself, the enzyme significantly enhances the user's natural abilities. Speed, strength, and stamina are all increased. It also grants a resistance to Wraith stunners. The enzyme acts like a narcotic, causing loss of judgment and addiction if taken over a long period or if too much is taken at one time. Withdrawal symptoms depend on the time and level of exposure to the enzyme; regulated use over a few days will cause severe fatigue in withdrawal, while months of dependency can potentially be fatal.
Aiden Ford became addicted to the enzyme after a Wraith that had begun to feed on him was killed. A sudden explosion caused it to flood his system with the enzyme. Made irrational by the enzyme, Ford stole Carson Beckett's entire supply and fled Atlantis to sustain his addiction, rather than allow Carson to wean him off the enzyme. Ford continued to hunt Wraith to collect more enzyme, believing that it made him a better soldier and was the key to defeating the Wraith. He eventually recruited his own small army using Pegasus humans, all of whom began taking the enzyme. His group captured AR-1, hoping to make their case to Atlantis through John Sheppard. The rest of his team was given the enzyme, while Sheppard was left alone to be an unbiased witness. They staged an ill-fated raid on a Hive ship, which saw the deaths of Ford's entire team, and presumably Ford himself. He is later shown to have survived, but the withdrawal, which he only survived with the help of a Wraith worshipper who knew how to treat it as a result, took him over a year to recover from. Sheppard believes that some of the populations of the Pegasus galaxy are advanced enough to be aware of the properties of the enzyme, including the negative effects and is thus why no one has ever used it in a similar manner to Ford. (SGA: "The Siege, Part 3", "The Lost Boys", "The Hive", "The Third Path")
A type of Wraith enzyme, though probably not related to the feeding enzyme, was part of a series of weekly injections given to a clone of Carson Beckett, which halted the necrosis of his body. (SGA: "The Kindred, Part 2")
In an Alternate reality visited by SG-1, Colonel Marshall Sumner and most of the expedition military were addicted to the enzyme to try and help them defend the ruined city they had taken as a new base from the Wraith. Sumner believed that they had been able to alter the enzyme to limit the more psychologically dangerous side-effects, but a Wraith Queen noted that many civilisations have attempted such an experiment and failed, with Sumner demonstrating increased paranoia and a refusal to take orders from General O'Neill (albeit 'justifying' it due to the anomaly of O'Neill being from a parallel universe and thus technically not in Sumner's chain of command). After a Wraith raid killed Sumner and other key members of the military, Major John Sheppard was able to re-take command and start weaning the survivors off the enzyme. (Stargate SG-1: Ouroboros)