However, later in the day, UP bowlers made inroads and left Karnataka teetering at 168/4 despite a strong opening stand by Karnataka openers, as the hosts still trail by 113 runs with six wickets in hand.
The fight on Thursday will be to grab the crucial first-innings lead.
Uttar Pradesh resumed their innings on 232/5, with Mohammed Saif (80 off 181 balls, 11x4) and Saurabh Kumar (27 off 37 balls; 5x4) at the crease. However, UP lost Saurabh Kumar early as he gave a catch to J Suchith off pacer Ronit More, as the visitors lost their sixth wicket with 250 on the board.
Then Mithun (6-60), who had taken three wickets on the opening day, ran through their lower order to scuttle them out for 281.
Mithun's scalps on Wednesday included rival stumper Upendra Yadav (3), Mohit Jangra (6) and Mohammed Saif, who played a valiant knock and added 24 runs to his overnight total. He, however, was devoid of partners.
Courtesy Mithun's show, Karnataka ensured that UP could add only 49 runs to their overnight score. Mithun was ably aided by another inform speedster More (2-41), who broke the stand between Saif and Saurabh Kumar, and leg-spinner Shreyas Gopal (2-51).
In reply, Karnataka openers Devdutt Padikkal (74 off 108 balls, 10x4) and Dega Nischal (36 off 90 balls; 4x4) conjured a strong 91-run stand for the first wicket. The two frustrated the UP bowlers before slow-left arm orthodox bowler Saurabh Kumar castled Nischal to send him back to the pavilion.
However, UP pegged back the hosts, taking three quick wickets to leave them teetering at 4-144. One-down Ravikumar Samarth (11), skipper Karun Nair (13) fell in quick succession.
Jangra then dismissed Padikkal, who hit 10 boundaries. Then Abhishek Reddy (23 not out) and Shreyas Gopal (8 not out) ensured that there was no further damage and remained unbeaten when stumps were drawn.
In another game at Visakhapatnam, test specialist Cheteshwar Pujara struck a patient unbeaten half century against Railways for Saurashtra. Pujara is batting on 69 off 136 balls with Arpit Vasavada (11 not out) as their side trails by only 37 runs after dismissing Railways for a paltry 248.
Uttar Pradesh 281 all out (Aryan Juyal 109, Mohammed Saif 80; Abhimanyu Mithun 6-60, Ronit More 2-41) versus Karnataka 168/4 (Devdutt Padikkal 74, Dega Nishal 36; Mohit Jangra 2-36).
Karnataka trailed by 113 runs.
Himachal Pradesh 158 and 133/7 (Sumeet Verma 36; Rishi Dhawan 27 batting; T Natarajan 2-11; R Ashwin 2-50) versus Tamil Nadu 96 (R Ashwin 24, J Kousik 21; Vaibhav Arora 3-21, Mayank Dagar 2-17).
Himachal Pradesh led by 195 runs.
Madhya Pradesh 125 and 118/3 (Anand Bais 45, Rameez Khan 41; Krunal Pandya 1-10) versus Baroda 222 (Yusuf Pathan 76 not out, Krunal Pandya 64; Mihir Hirwani 4- 21, Avesh Khan 4-69).
Madhya Pradesh led by 21 runs.
Railways 248 (Pratham Singh 98, Karn Sharma 52; Jaydev Unadkat 4-56, Prerak Mankad 2-33) versus Saurashtra 211-3 (Cheteshwar Pujara 69 not out; Snell Patel 46; Karn Sharma 1-45).
Saurashtra trailed by 37 runs.