mmseq: 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/mmseq - from package: mmseq

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

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