Author/Editor		Božič, Mojca
Title		Kaj je homocistein?
Translated title		What is homocysteine?
Type		članek
Source		Farm Vestn
Vol. and No.		Letnik 53, št. Poseb št
Publication year		2002
Volume		str. 337-41
Language		slo
Abstract		Homocysteine is a thiol-containing aminoacid produced as an intermediate in methionine metabolism. It is further metabolised into cystathionine (trans-sulphuration pathway) by cystathionine-(beta-synthase with vitamin B6 as a cofactor. Another metabolic pathway is remetilation of homocysteine into methionine by methionine synthase with vitamin B12 as a cofactor and methyletetrahydrofolate as the methyl donor. In addition, in the liver betaine serves as a methyl donor and this reaction is catalysed by betaine homocystein methyltransferase. Absent or diminished activity of enzymes, which participate in homocysteine metabolism, or absence of vitamins B12, B6 or folate cause accumulation of homocysteine - the so called hyperhomocysteinemia. Hyperhomocysteinemia is associated with vascular diseases, pregnancy complications, some of the inherited abnormalities, neuropsychiatric disturbances and cognitive impairment in the elderly.
Summary		Homocistein je tiolna aminokislina, ki nastaja kot intermediat v presnovi metionina. Presnavlja se v cistationin (transsulfuracijska pot), pri čemer reakcijo katalizira cistationin-beta-sintaza, kofaktor reakcije pa je vitamin B6. Druga presnovna pot je remetilacija homocisteina v metionin. To reakcijo katalizira metionin-sintaza, kofaktor je vitamin B12 donor metilne skupine pa metil-tetrahidrofolat. V jetrih je donor metilne skupine tudi betain, to reakcijo pa katalizira betain-homocistein-metil-transferaza. Odsotna ali zmanjšana aktivnost encimov, ki sodelujejo v presnovi homocisteina, ali pomanjkanje vitaminov B12 B6 ali folata povzročijo kopičenje homocisteina, t. i. hiperhomocisteinemijo. Hiperhomocisteinemija je povezana z žilnimi boleznimi, zapleti v nosečnosti, nekaterimi prirojenimi motnjami, nevropsihiatričnimi motnjami in kognitivnimi motnjami starejših oseb.
Descriptors		HOMOCYSTEINE CYSTATHIONINE BETA-SYNTHASE METHYLENETETRAHYDROFOLATE DEHYDROGENASE