Four of them are classified as type I membrane proteins, MMP-14, MMP-15, MMP-16 and MMP-24, while remaining two (MMP-17 and MMP-25) are attached to the membrane by glycosylphosphatidylinositol molecule.
Transmembrane metalloproteinases, MMP-14,MMP-15 and MMP-16 were considered to be expressed to a significant level in the course of renal cell carcinoma in tumour-modified tissue and present in urine samples collected from the same patients .
Metalloproteinases include cell membrane metalloproteinases which are related to cell membrane (MMP-14, MMP-15, MMP-16
, and MMP-17), gelatinases (MMP-2 and MMP-9), stromelysins (MMP-3, MMP-7, MMP-10, MMP-11, and MMP-12), and collagenases (MMP-1, MMP-8, and MMP-13).
They are classified according to their substrate specificity, sequence similarity, and domain organization into six groups: collagenases (MMP-1, MMP8, MMP-13, and MMP-18), gelatinases (MMP-2, MMP9), stromelysins (MMP-3, MMP-10), matrilysins (MMP7, MMP-26), membrane-type MMPs (MMP-14, MMP-15, MMP-16
, MMP-24, MMP-17, and MMP-25), and other MMPs (MMP-12, MMP-19, MMP-20, MMP-21, MMP-23, MMP-27, and MMP-28) .
Membrane type MMPs (MT-MMP) (MMP-14, MMP-15, MMP-16
, MMP-17, MMP24, and MMP-25) are anchored to the plasma membrane by a transmembrane domain with a cytoplasmic domain or a glycosylphosphatidylinositol (GPI).
Membrane-type (MT)-MMPs consist of four transmembrane MMPs, MMP-14 (MT1-MMP), MMP-15 (MT2-MMP), MMP-16
(MT3-MMP), and MMP-24 (MT5MMP) and two glycosyl-phosphatidylinositol-anchored MMPs, MMP-17 (MT4-MMP) and MMP-25 (MT6-MMP).
As MMPs pertencem a classe metalo, dependem de zinco para a sua acao catalitica e sao classificadas em cinco grupos: colagenases (MMP-1, MMP-8, MMP-13, MMP-18), gelatinases (MMP-2 e MMP-9), estromalisinas (MMP-3, MMP-10, MMP-11), MMPs tipo membrana (MMP-14, MMP-15, MMP-16
, MMP-17, MMP-24, MMP-25) e outros (MMP-7, MMP-12, MMP-20 e MMP-26) (Tabela 1) (9, 12, 13).