Kerber led a set and a break only to see the world No.89 edge her way back into the contest, with six straight points securing the tiebreak 7-3.
"One is right and the other one is left-handed".
Bidding to be the first woman to defend her Australian title since Victoria Azarenka in 2013, Kerber had an indifferent lead-up to Melbourne with early exits in Brisbane and Sydney this month. However, Kerber rebounded to win the next four games before closing out the victory.
Venus Williams reached the Australian Open third round for a 13th time with a 6-3 6-2 victory over Swiss qualifier Stefanie Voegele in Melbourne. "I am truly sorry and look forward to returning in 2017". "But at the end, I'm happy that I won the match", said the world number one.
Witthoeft, who had lost both her previous matches to Kerber, skewed a forehand wide on match point, then went to the net, shook hands and gave her fellow German a kiss on each cheek.
As against Tsurenko, Kerber wrapped up the first set quickly but was knocked off her stride by the free-swinging Witthoeft, who began finding the lines after a wayward start. "But overall I feel like I am getting better with every passing day. But I picked it up and I played great the fifth set". Kerber was rattled and lost her opening service game to love, but she quickly regrouped as the crowd got behind her to break back.
Romania's Sorana Cirstea stunned 10th-seeded Carla Suarez Navarro of Spain 7-6 (1), 6-3, while Germany's Mona Barthel took down 29th-seeded Monica Puig of Puerto Rico 6-4, 6-4. "But today I was doing a few more mistakes", said Kerber, who next plays another left-hander in 58th-ranked Czech Kristyna Pliskova, the twin sister of U.S. Open finalist Karolina.
The 11th seed Elina Svitolina won the most important points against Julia Boserup to notch a 6-4 6-1 triumph.
No. 24 seed Anastasia Pavlyuchenkova got past Russian countrywoman Natalia Vikhlyantseva 6-2, 6-2 in another second-round match.
On the men's side, Roger Federer advanced to the third round by beating Noah Rubin 7-5, 6-3, 7-6 (3) to keep intact his record of never having failed to reach the third round at the 18 Australian Opens he's played in.
There was better news for Venus Williams, a 6-3 6-2 victor over Stefanie Voegele, and French Open title-holder Garbine Muguruza, who defeated Samantha Crawford 7-5 6-4.