Guthrie finished fifth in the Shriners Hospitals for Childrens' Open on Sunday after a closing 64 and carried on where he left off at Lake Malaren.
The 23-year-old, who only turned professional last year, carded birdies at the second, third and seventh to reach the turn in 33, before also picking up shots on the 13th and 14th.
In the windy conditions that was enough for a two-shot lead over a group of players including fellow American John Daly, the former Open champion three under with two holes to play.
Spanish pair Pablo Larrazabal and Gonzalo Fernandez-Castano were also three under after 13 and 10 holes respectively, alongside Thailand's Thongchai Jaidee, who had reached the turn in 33.
This week's event is the first of four tournaments which make up the inaugural Final Series on the European Tour, with Sweden's Henrik Stenson holding a lead of 425,573 euros (£362,660) over Graeme McDowell at the top of the Race to Dubai.
But with a first prize of 850,000 euros (£725,000) on offer here and a total prize fund of almost £20million in the four events, the battle to become European number one in Dubai in mid-November is far from over.
Stenson, whose victory in the Tour Championship in Atlanta last month secured a £6.2million bonus for winning the FedEx Cup, was one over par through six holes after three-putting the fifth, while McDowell was level par after a birdie on the third was cancelled out by a bogey on the next.
Former world number ones Rory McIlroy, Lee Westwood and Luke Donald were all level par, McIlroy's birdie on the second having been followed by a three-putt bogey on the fourth.
Meanwhile, Holland's Joost Luiten - twice a winner on the European Tour this season - had been forced to withdraw with a shoulder injury.