Highly Active Soluble Processed Forms of the Transglutaminase 1 Enzyme in Epidermal Keratinocytes

• Published in: The Journal of biological chemistry 1995-07, Vol.270 (30), p.18026-18035
• Main Authors: Kim, S Y, Chung, S I, Steinert, P M
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Cells, Cultured; Cytosol - enzymology; Epidermal Cells; Epidermis - enzymology; Half-Life; Humans; Hydrolysis; Isoenzymes - chemistry; Isoenzymes - metabolism; Keratinocytes - enzymology; Molecular Sequence Data; Protein Processing, Post-Translational; Sequence Alignment; Solubility; Transglutaminases - chemistry; Transglutaminases - metabolism
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.270.30.18026

The transglutaminase 1 (TGase 1) enzyme is required for the formation of a cornified cell envelope in epidermal keratinocytes. We show here that in addition to its membrane-anchored form, soluble forms of it are also important in keratinocytes. Proliferating cells contain soluble full-length enzyme of 106 kDa, but terminally differentiating cells contain a soluble 67-kDa form often complexed with a 33-kDa protein as well. The amino terminus of the 67 kDa form is residue 93 of the TGase 1 protein, corresponding to the site of proteolytic activation of the factor XIIIa TGase. The amino terminus of the 33-kDa protein is residue 573, corresponding to the site of a second proteolytic cleavage site of factor XIIIa, and of the site for proteolytic activation of the TGase 3 enzyme. The specific activity of the 67/33-kDa soluble complex is twice that of the soluble 67-kDa form and 10 times that of full-length TGase 1. The half-lives of the 67/33- and 106-kDa forms are about 7 or 20 h, respectively. Thus the TGase 1 enzyme is complex, since it exists in keratinocytes as multiple soluble forms, either intact or proteolytically processed at conserved sites, and which have varying specific activities and likely functions.