Katayama, characterized by his trademark cowboy hat, fired a Friday 64 to move to 9-under-par 131, one shot clear of Mickelson.
Jim Furyk also shot 64 to move to 6-under, three off the lead. Hes tied at 6-under with K.J. Choi. Choi bogeyed three of his first four holes Friday, but recovered to shoot 68.
Furyks playing companion, Mark OMeara established a new course record and tied a major championship record by carding a 7-under-par 63. The 1998 Masters and British Open champion is at 5-under.
Two-time defending champion Tiger Woods started the second round tied for 100th place following a 3-over-par 73. He teed off with David Duval and Retief Goosen at 1:50 p.m. ET.
Duval, the 2001 British Open winner, opened in 4-under 66; while reigning U.S. Open champion Goosen shot 1-under 69.
Not everyone fared well in the morning. Overnight leader Grant Waite was ten shots higher on Friday than in round one. The New Zealander shot 4-over 74 to fall to 2-under for the tournament.
Sergio Garcia followed an opening 68 with a Day-Two 75. The 21-year-old Spaniard will not make the cut at 3-over-par.
Neither will John Daly. Ten years ago, Daly shocked the golfing world by winning the PGA Championship at Crooked Stick as the ninth alternate. This year, Daly shot 72-77 to finish 36 holes at 9-over-par.
Katayama is a nine-time winner on the Japanese Tour. Friday, he bogeyed his second hole of the day, but birdied four of his final five coming home.
Mickelson once again recorded five birdies and one bogey.
Im eliminating the mistakes, Mickelson said. If I can continue to do that, I like my chances over the next two days.
Full-field scores from the 83rd PGA Championship