Pompey need only two more points from their remaining games for their best total in the Premier League in what has been a magnificent season for the FA Cup semi-finalists.
Harry Redknapp's men weathered a second-half storm to continue their push for a Uefa Cup place on two fronts.
Utaka and the inventive Niko Kranjcar were particularly impressive, while Defoe continued his prolific form and proved to be the difference between the two sides.
Wigan - without the suspended midfield trio of Michael Brown, Wilson Palacios and Jason Koumas - had plenty of possession but were profligate in front of goal.
Portsmouth could have gone ahead after just 10 minutes, with Hermann Hreidarsson forcing Chris Kirkland into an early save and Defoe shooting over the crossbar after a Wigan defensive mix-up inside the box.
Wigan were not without their chances, however. Indeed, the visitors would certainly have taken a 15th-minute lead had Johnson not saved the day for Portsmouth.
The right-back rushed back to scoop Valencia's goal-bound shot onto the crossbar, and consequently to safety.
Taylor then struck from the inside the D and was just inches wide of the target.
Portsmouth went ahead thanks to Defoe's seventh goal for the club.
Utaka surging run into the box caused panic among the Wigan defence; the Nigerian tried his luck at goal but his shot deflected off Kevin Kilbane and into the path of the deadly Defoe who finished with aplomb.
Seconds later and Kranjcar forced Kirkland to dive high to his left to thwart the Croatian's vicious long-range effort.
Once Portsmouth went ahead - they are the only club in the top flight holding a 100% record when scoring first - Wigan could have been forgiven for conceding defeat.
But the visitors returned from the break with added vigour and should have equalised when referee Alan Wiley harshly awarded a penalty for Distin's nudge on Valencia.
Taylor stepped up to the spot but his effort was too close to James. The England goalkeeper parried the ball back to Taylor but the former Tranmere defender blasted the rebound into the stands.
Bruce's men dominated, but they were unable to beat the imposing James.
Antoine Sibierski put Emile Heskey through only for James to come quickly off his line and smother the ball. Sibierski then forced the former Liverpool goalkeeper into a fine save with a dipping volley.
Portsmouth were largely anonymous in the closing stages, but moments before the end Kranjcar's defence-splitting pass allowed Defoe to beat the hapless Kirkland from 18 yards.
Harry Redknapp on David James:
"Without a top, top keeper you are nothing and he's the best one around at the moment.
"For me he's the [Cristiano] Ronaldo of goalkeepers, someone who does that little bit special.
"When I knew there was a chance of signing him I jumped at it."
Wigan manager Steve Bruce:
"We created five or six chances and deserved something out of the game but we made nothing of them.
"We've got four games out of six left at home, though, and I think a couple of wins will see us all right.
"I think 35 points might keep a team up this season."
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