g_enemat: 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/g_enemat - from package: gromacs

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

On Debian possible default full paths are:

/usr/bin/g_enemat - from package: gromacs

You may install the required package with command apt-get install {package}

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