Myrosinase-dependent and -independent formation and control of isothiocyanate products of glucosinolate hydrolysis.
Brassicales contain a myrosinase enzyme that hydrolyzes glucosinolates to form toxic isothiocyanates (ITC), as a defense against bacteria, fungi, insects and herbivores including man. Low levels of ITC trigger a host defense system in mammals that protects them against chronic diseases. Because humans typically cook their brassica vegetables, destroying myrosinase, there is a great interest in determining how human microbiota can hydrolyze glucosinolates and release them, to provide the health benefits of ITC. ITC are highly reactive electrophiles, binding reversibly to thiols, but accumulating and causing damage when free thiols are not available. We found that addition of excess thiols released protein-thiol-bound ITC, but that the microbiome supports only poor hydrolysis unless exposed to dietary glucosinolates for a period of days. These findings explain why 3-5 servings a week of brassica vegetables may provide health effects, even if they are cooked.
Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign , Urbana, IL, USA.
Donato
D
Angelino
Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign , Urbana, IL, USA.
Edward B
EB
Dosz
Food Composition and Methods Development Laboratory, Beltsville Human Nutrition Research Center, Agricultural Research Service, U.S. Department of Agriculture , Beltsville, MD, USA.
Jianghao
J
Sun
Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign , Urbana, IL, USA.
Jennifer L
JL
Hoeflinger
Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign , Urbana, IL, USA.
Maxwell L
ML
Van Tassell
Food Composition and Methods Development Laboratory, Beltsville Human Nutrition Research Center, Agricultural Research Service, U.S. Department of Agriculture , Beltsville, MD, USA.
Pei
P
Chen
Food Composition and Methods Development Laboratory, Beltsville Human Nutrition Research Center, Agricultural Research Service, U.S. Department of Agriculture , Beltsville, MD, USA.
James M
JM
Harnly
Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign , Urbana, IL, USA.
Michael J
MJ
Miller
Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign , Urbana, IL, USA.
Elizabeth H
EH
Jeffery
glucosinolate hydrolysis; isothiocyanate; microbiome; myrosinase; sulforaphane; thiol binding