Table 1.

The extra- and intra- intestinal sources of mTG or tTG-like activity in the human gut. (Adapted from ref. [7,12,13,14]). mTG-microbial transglutaminase, tTG-tissue transglutaminase.

MTG Source		Reference
Extra-Intestinal	Processed food additive	[6,8,9,11,12,13,14,20]
	Pathobionts	[24,25,26]
	Probiotics	[27,28]
	Plants	[29,30]
	Vegetables	[31]
	Meat	[32,33]
Intra-Intestinal	Microbiome	[7,12,13,14,24,25]
	Dysbiome	[7,12,13,14,24,25]
	Yeasts	[34,35,36]
	Fungi	[37,38]
	Viruses	[15,16,17,18]