mturk: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/mturk - from package: python2-boto
/usr/bin/mturk - from package: python-boto

You may install the required package with command yum install {package}

Error in other languages:
mturk: bevel nie gevind nie
mturk: comandă negăsită
mturk: comando não encontrado
mturk: commande introuvable
mturk: command not found
mturk: käsku ei ole
mturk: không tìm thấy lệnh
mturk: komanda nerasta
mturk: Kommando nicht gefunden.
mturk: kommandot finns inte
mturk: komut yok
mturk: nie znaleziono polecenia
mturk: níor aimsíodh an t-ordú
mturk: no se encontró la orden
mturk: no s'ha trobat l'ordre
mturk: opdracht niet gevonden
mturk: parancs nem található
mturk: perintah tidak ditemukan
mturk: príkaz nenájdený
mturk: příkaz nenalezen
mturk: команда не найдена
mturk: командата не е открита
mturk: 命令找不到
mturk: コマンドが見つかりません