To　cope　with　the　low　latency　requirements　and　security　issues　of　the　emerging　applications　such　as　Internet　of　Vehicles　(IoV)　and　Industrial　Internet　of　Things　(IIoT),　the　blockchain-enabled　Mobile　Edge　Computing　(MEC)　system　has　received　extensive　attention.　However,　blockchain　is　a　computing　and　communication　intensive　technology　due　to　the　complex　consensus　mechanisms.　To　facilitate　the　implementation　of　blockchain　in　the　MEC　system,　this　paper　adopts　the　committee-based　Practical　Byzantine　Fault　Tolerance　(PBFT)　consensus　algorithm　and　focuses　on　the　committee　selection　problem.　Vehicles　and　IIoT　devices　generate　the　transactions　which　are　records　of　the　application　tasks.　Base　Stations　(BSs)　with　MEC　servers,　which　serve　the　transactions　according　to　the　wireless　channel　quality　and　the　available　computing　resources,　are　blockchain　nodes　and　candidates　for　committee　members.　The　income　of　transaction　service　fees,　the　penalty　of　service　delay,　the　decentralization　of　the　blockchain　and　the　communication　complexity　of　the　consensus　process　constitute　the　performance　index.　The　committee　selection　problem　is　modeled　as　a　Markov　decision　process,　and　the　Proximal　Policy　Optimization　(PPO)　algorithm　is　adopted　in　the　solution.　Simulation　results　show　that　the　proposed　PPO-based　committee　selection　algorithm　can　adapt　to　the　system　design　requirements　with　different　emphases　and　outperforms　other　comparison　methods.