Abstract
L-homoarginine (hArg) is a non-coding amino acid, the blood level reduction of which is associated with an increased risk of stroke and heart attack. In humans and animals, hArg is mainly formed during the reaction catalyzed by the enzyme of the metabolic pathway of creatine biosynthesis:arginine: glycine amidotransferase (AGAT, EC 2.1.4.1), in the case where L-lysine acts instead of glycine as an acceptor of the arginine amidine group. It has been shown that hArg can serve for nitric oxide biosynthesis which is seemed a single significant enzymatic pathway established for hArg. The aim of this study was to investigate hArg as a substrate human AGAT and arginases. Materials and methods. In experiments with recombinant enzymes we established that Km for hArg in the reaction catalyzed by AGAT towards the formation of guanidinoacetic acid is 12.0 ± 1.1 mM. In reactions catalyzed by both types of arginase activity against hArg, unlike arginine, was not detected. Conclusions. Thus, the present study established that hArg may be considered as a substrate of AGAT additionally to nitric oxide synthases. Metabolic value of hArg, in addition to regulation of vascular tone, can be associated with cell energy metabolism. According to our data a decrease of hArg blood levels in cardiovascular diseases appears to be unrelated to a detectable increase of arginase activity.
Highlights
L-homoarginine is a non-coding amino acid, the blood level reduction of which is associated with an increased risk of stroke and heart attack
HArg is mainly formed during the reaction catalyzed by the enzyme of the metabolic pathway of creatine biosynthesis:arginine: glycine amidotransferase (AGAT, EC 2.1.4.1), in the case where L-lysine acts instead of glycine as an acceptor of the arginine amidine group
In experiments with recombinant enzymes we established that Km for hArg in the reaction catalyzed by arginine: glycine aminotransferase (AGAT) towards the formation of guanidinoacetic acid is 12.0 ± 1.1 mM
Summary
Для цитирования: Алексеевская Е.С., Субботина Т.Ф., Жлоба А.А. Гомолог аргинина гомоаргинин в качестве субстрата аргинин:глицинамидинотрансферазы и аргиназ человека. Гомолог аргинина гомоаргинин в качестве субстрата аргинин: глицинамидинотрансферазы и аргиназ человека. В организме человека и животных гАрг образуется преимущественно в ходе реакции, катализируемой ферментом метаболического пути биосинтеза креатина – аргинин:глицинамидинотрансферазой (АГАТ, КФ 2.1.4.1), в случае, когда акцептором амидиновой группы аргинина вместо глицина выступает L-лизин. 1. Известные и предполагаемые реакции, катализируемые аргинин:глицинамидинотрансферазой (АГАТ): а – основная реакция, образование предшественника креатина (гуанидинуксусной кислоты); b – реакция образования гомоаргинина из аргинина и лизина; с – предполагаемая реакция, в которой в качестве донора амидиновой группы выступает гомоаргинин Fig. 1. В силу обратимости реакций, катализируемых АГАТ [9, 10], логично предположить, что метаболическое значение гАрг, особенно в условиях введения больших количеств данной аминокислоты, может быть связано с непосредственным участием в синтезе гуанидинуксусной кислоты в качестве донора амидиновой группы вместо аргинина Цель работы – оценить гАрг в качестве субстрата для АГАТ и аргиназ I, II типов
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