WASHINGTON (Reuter) - Garlic`s strong smell holds the secret to its remarkable antimicrobial powers, Israeli researchers reported on Tuesday. Serge Ankri of the Weizmann Institute of Science and colleagues found that allicin, the active ingredient in garlic that makes it pungent, blocks certain enzymes in the amoebas that can cause dysentery. Working with hamsters, they said the amoebas were unable to cause the problems that lead to dysentery. "Our present findings shed more light on the remarkable mode of action of allicin on Entamoeba histolytica, and lend further support to the reasons for the widespread use of allicin and fresh garlic extracts since ancient times as broad-spectrum, natural antimicrobial agents," they said in a statement. The enzymes blocked by allicin include cysteine proteinases, which infectious organisms use to damage and invade tissues, and alcohol dehydrogenase enzymes, which help the organisms digest food. Ankri`s group said many bacteria, fungi, and viruses used the same enzymes. In a second study the Weizmann researchers found that allicin worked against the enzymes by reacting with sulfhydryl (SH) groups, or thiols - important components of the enzymes. Thiols help in the body`s synthesis of cholesterol, and the researchers said this could be why garlic is reputed to help lower cholesterol. "It has been suggested that garlic lowers the level of harmful cholesterol, and our study provides a possible explanation for how this may occur," Meir Wilchek, dean of the institute`s biochemistry faculty, said. "However, more research is necessary to establish what role allicin might play in preventing the clogging up of arteries."