Template:Leucine metabolism in humans and Template:Leucine metabolism in humans/sandbox: Difference between pages

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| header = {{{header|{{when pagename is|Β-Hydroxy β-methylbutyric acid=Biosynthesis and metabolism of β-hydroxy β-methylbutyrate in humans|Leucine=Leucine metabolism in humans|other=[[Leucine#Metabolism in humans|Leucine metabolism in humans]]}}}}}

| caption = {{{caption|Human [[metabolic pathway]] for {{no selflink|β-Hydroxy β-methylbutyric acid|HMB}} and {{No selflink|isovaleryl-CoA}} relative to {{No selflink|leucine|{{nowrap|{{smallcaps all|L}}-leucine}}}}.{{when pagename is|Β-Hydroxy β-methylbutyric acid=<ref name="ISSN position stand 2013" /><ref name="HMB athletic performance-related effects 2011 reviewb" /><ref name="Leucine metabolism" />|other=<ref name="ISSN position stand 2013">{{cite journal | vauthors = Wilson JM, Fitschen PJ, Campbell B, Wilson GJ, Zanchi N, Taylor L, Wilborn C, Kalman DS, Stout JR, Hoffman JR, Ziegenfuss TN, Lopez HL, Kreider RB, Smith-Ryan AE, Antonio J | title = International Society of Sports Nutrition Position Stand: beta-hydroxy-beta-methylbutyrate (HMB) | journal = Journal of the International Society of Sports Nutrition | volume = 10 | issue = 1 | pages = 6 | date = February 2013 | pmid = 23374455 | pmc = 3568064 | doi = 10.1186/1550-2783-10-6 | doi-access = free }}</ref><ref name="HMB athletic performance-related effects 2011 reviewb">{{cite journal | vauthors = Zanchi NE, Gerlinger-Romero F, Guimarães-Ferreira L, de Siqueira Filho MA, Felitti V, Lira FS, Seelaender M, Lancha AH | title = HMB supplementation: clinical and athletic performance-related effects and mechanisms of action | journal = Amino Acids | volume = 40 | issue = 4 | pages = 1015–1025 | date = April 2011 | pmid = 20607321 | doi = 10.1007/s00726-010-0678-0 | s2cid = 11120110 | url = https://repositorio.unal.edu.co/handle/unal/77957 | quote = HMB is a metabolite of the amino acid leucine (Van Koverin and Nissen 1992), an essential amino acid. The first step in HMB metabolism is the reversible transamination of leucine to [α-KIC] that occurs mainly extrahepatically (Block and Buse 1990). Following this enzymatic reaction, [α-KIC] may follow one of two pathways. In the first, HMB is produced from [α-KIC] by the cytosolic enzyme KIC dioxygenase (Sabourin and Bieber 1983). The cytosolic dioxygenase has been characterized extensively and differs from the mitochondrial form in that the dioxygenase enzyme is a cytosolic enzyme, whereas the dehydrogenase enzyme is found exclusively in the mitochondrion (Sabourin and Bieber 1981, 1983). Importantly, this route of HMB formation is direct and completely dependent of liver KIC dioxygenase. Following this pathway, HMB in the cytosol is first converted to cytosolic β-hydroxy-β-methylglutaryl-CoA (HMG-CoA), which can then be directed for cholesterol synthesis (Rudney 1957) (Fig. 1). In fact, numerous biochemical studies have shown that HMB is a precursor of cholesterol (Zabin and Bloch 1951; Nissen et al. 2000).<!--<br /><br /> In the second pathway, after transamination, [α-KIC] in liver generates isovaleryl-CoA through the enzymatic action of branched-chain ketoacid dehydrogenase (BCKD) and after several steps, there is production of HMG-CoA through the enzyme HMG-CoA synthase (Fig. 1). Under normal conditions the majority of KIC is converted into isovaleryl-CoA, in which approximately 5% of leucine is metabolized into HMB (Wilson et al. 2008; Van Koverin and Nissen 1992). However, Nissen and Abumrad (1997) provided evidence that the primary fate of HMB is probably conversion to HMG-CoA in the liver, for cholesterol biosynthesis.--> }}</ref>{{when pagename is|Leucine=<ref name="Leucine metabolism" />|other=<ref name="Leucine metabolism">{{cite book | vauthors=Kohlmeier M | title=Nutrient Metabolism: Structures, Functions, and Genes | date=May 2015 | publisher=Academic Press | isbn=978-0-12-387784-0 | pages=385–388 | edition=2nd | section-url=https://books.google.com/books?id=aTQTAAAAQBAJ&q=beta-hydroxy%20beta-methylbutyrate%20HMB&pg=PA387 | url=https://books.google.com/books?id=aTQTAAAAQBAJ | access-date=6 June 2016 | section=Leucine | quote= Energy fuel: Eventually, most Leu is broken down, providing about 6.0kcal/g. About 60% of ingested Leu is oxidized within a few hours&nbsp;... Ketogenesis: A significant proportion (40% of an ingested dose) is converted into acetyl-CoA and thereby contributes to the synthesis of ketones, steroids, fatty acids, and other compounds}}<br />[https://books.google.com/books?id=aTQTAAAAQBAJ&pg=PA386#v=onepage&q&f=false Figure 8.57: Metabolism of {{smallcaps all|L}}-leucine]</ref>}}}} Of the two major pathways, {{nowrap|{{smallcaps all|L}}-leucine}} is mostly metabolized into isovaleryl-CoA, while only about&nbsp;5% is metabolized into HMB.<ref name="ISSN position stand 2013" /><ref name="HMB athletic performance-related effects 2011 reviewb" /><ref name="Leucine metabolism" />}}}

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