This is who will be testifying on Day One of the Commission of Inquiry into State Capture on Monday and the reasons they may have been asked to appear before Deputy Chief Justice Ray Zondo.Willie MathebulaHe was appointed acting chief procurement officer (CPO) at National Treasury by then finance minister Malusi Gigaba in September 2017. The office of the chief procurement officer is one of the most important gatekeepers at Treasury because it oversees the government's annual spend on goods and services of around R840 billion. Before he became acting CPO, he was the Office of the Chief Procurement Officer's link with state-owned companies.Mcebisi JonasMcebisi Jonas (Gallo Images / Daily Sun / Jabu Kumalo)He was the man who blew the lid off the alleged Guptas' brazen attempts to capture the South African state. The former deputy minister of finance shocked the country in early 2016 when he claimed the Guptas offered him R600 million in cash to pacify Treasury. He was also promised the Minister of Finance job. Jonas, along with then finance minister Pravin Gordhan, attempted to fortify Treasury against looting, but was fired by then president Jacob Zuma in March 2017.READ: #StateCaptureReport: Guptas offered me R600k in cash - JonasVytjie MentorThe veteran ANC MP told the public protector she was flown up from Cape Town and taken to the Guptas' Saxonwold compound in Johannesburg where she was offered the job of Minister of Public Enterprises. She would have then overseen all state-owned enterprises, the scene of much looting by Gupta aligned acolytes. She refused the overture and said after she did so, Zuma appeared from another room in Saxonwold and said: "Don't worry, ntombazana, everything will be okay."Themba MasekoThemba Maseko (Gallo Images / Alet Pretorius)Much respected as Cabinet spokesperson, Maseko was also the head of the Government Communications and Information System and in charge of all state advertising spend. Zuma allegedly called him to request that he assist the Guptas in whatever way possible and Ajay Gupta apparently started to badger Maseko to divert government advertising expenditure to their media company. Maseko was fired after he refused to bow to Zuma's friends. Phumla Williams She was in charge of all government communications during the mourning period after former president Nelson Mandela's death and has been acting in Maseko's former position in the recent past. She has deep knowledge of the internal machinations of the state.