Prathap, 70, who began his acting career with Bharathan's Malayalam film Aaravam in 1978, went on to star in many significant titles in the language including Thakara (1979), Aarohanam (1979), Chamaram (1980), 22 Female Kottayam (2012) and Bangalore Days (2014). He made his Tamil acting debut with 1979 film Azhiyadha Kolangal. The Balu Mahendra coming-of-age drama also co-starred Shoba and Kamal Haasan in lead roles. But his turning point as an actor in Tamil was in yet another Balu Mahendra directorial starring Shoba – Moodu Pani. In the 1980 film, Prathap played the role of Chandru, a young serial killer on a mission to kill prostitutes. The film went on to become critically acclaimed, remembered till date for Ilaiyaraaja's music, Mahendra's complex screenplay and Prathap's layered performance.
Prathap followed this up with many other successful stints in the 80s including K Balachander's Varumayin Niram Sivappu (1980), Mahendran's Nenjathai Killathey (1980), and Santhana Bharathi and P Vasu's Panneer Pushpangal (1981). Apart from his acting prowess, Tamil cinema in the 80s also witnessed his directorial finesse with films such Meendum Our Kadhal Kadhai (1985) starring himself and Radikaa Sarathkumar, to whom he was briefly married in the 80s, and Jeeva, a 1988 action film starring Sathyaraj and Amala.
But a breakout film in his filmmaking oeuvre came in Kamal Haasan's Vetri Vizhaa. The 1989 action film co-starring Prabhu, Sasikala and Khushbu, was loosely based on author Robert Ludlum's spy thriller Bourne Identity. Pratap's last film as a director was 1997 Malayalam film Oru Yathramozhi, a father-son emotional drama starring Mohanlal and Sivaji Ganesan.
The actor then went on to play supporting roles in later films including Thedinen Vanthathu (1997), Mohanlal's award-winning film Thanmathra (2005), Vegam (2014), Remo (2016). Prathap was recently seen in many titles in the year 2020 such as Jyotika's Ponmagal Vandhal (in a moving performance as a judge), Tovino Thomas's Forensic, and Kamali From Nadukkaveri. The actor's last acting performance was in Mammootty's CBI5: The Brain (2022).