The Australia-raised pace bowler, in for injured Nottinghamshire colleague Ryan Sidebottom, had the dangerous Hashim Amla lbw for 38 but that was the only wicket the Proteas lost in the morning session.
At lunch, South Africa were 158 for four, a deficit of 45.
Ashwell Prince was 34 not out and AB de Villiers seven not out.
Former roof tiler Pattinson, who turns 30 next month, was born in the English east coast fishing town of Grimsby but was brought up in Australia.
He only made his senior debut for Australia state side Victoria last year, after several seasons with Melbourne club Dandenong, and came into this Test on the back of a career total of just 11 first-class matches.
Pattinson, who joined Nottinghamshire at the start of the season, caught the attention of the selectors with 29 first-class wickets in six matches this term for the Midlands county at 20.86 apiece.
It seemed he was heading for the same fate as now retired Gloucestershire pace bowler Mike Smith, whose Test career amounted to no more than a wicketless England debut at Headingley.
But Pattinson, the fourth seamer deployed by England captain Michael Vaughan on Saturday, made the breakthrough in his fourth over of the day when a full-toss hit Amla on the front pad.
It was a tight call for umpire Daryl Harper, with television replays suggesting the ball would have missed leg-stump.
However, the Australian official eventually raised his finger to leave the Proteas 147 for four and end a promising stand of 67 between Amla and Prince, both of whom made hundreds in the drawn first Test at Lord's.
Elated fielders swarmed round Pattinson who, for all the controversy surrounding his selection, appeared to have been accepted by the rest of Vaughan's men.
The wicket was the highlight of a spell which saw Pattinson take one wicket for 17 runs in six overs.
South Africa resumed on 102 for three, a deficit of 102 after fast bowlers Morne Morkel and Dale Steyn had taken four wickets apiece as England were dismissed for 203.
Amla, controversially reprieved by a belated third umpire intervention after Vaughan 'caught' him at mid-off, was 18 not out with Prince nine not out.
Vaughan opened the bowling with the all-Lancashire attack of James Anderson and Andrew Flintoff.
The two pacemen had, between them, taken all three wickets to fall on Friday, with Flintoff, in his first Test for 18 months because of injury, looking in particularly fine form.
Their combined initial seven overs on Saturday yielded just eight runs.
Pattinson meanwhile lingered in the outfield, having been given just three overs with the new ball on Friday, before his moment of glory.