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متابولیسم پروتئین ها و اسیدهای آمینه:
دکتر سلامی گروه بیوشیمی بالینی
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گردش پروتئین در بدن
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سرنوشت کاتابولیک اسیدهای آمینه
سرنوشت اسکلت کربنی سرنوشت عامل آمین
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سرنوشت عامل آمین آمونیاک آمونیاک ترکیب بسیار سمی برای بدن بوده و ازدیاد آن در خون سبب بروز پدیده هایپرآمونمی hyperammonemiaشده که سبب بروز علائم شدیدی در سیستم عصبی
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)TRANSAMINATIONترانس آمیناسیون اسیدهای آمینه (
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انتقال گروه آمین در بدن انسان
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The urea cycle also known as the ornithine cycle, is a cycle of biochemical reactions occurring in many animals that produces urea ((NH2)2CO) from ammonia (NH3). This cycle was the first metabolic cycle discovered (Hans Krebs and Kurt Henseleit, 1932), five years before the discovery of the TCA cycle. In mammals, the urea cycle takes place primarily in the liver, and to a lesser extent in the kidney.
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Step 1 First step combines CO2 and NH4+ to form carbamoyl phosphate
Reaction requires ATP and H2O Takes place in the mitochondria Catalyzed by carbamoyl phosphate synthase 22.8 The Urea Cycle
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گروه های آمین کاربامیل فسفات می تواند از منشاء ترکیبات زیر که به کبد می رسند تشکیل گردد:
مقدار اندکی آمونیاکی که از طریق سیاهرگ بابی به کبد می رسد. گلوتامین که عامل آمین حاصل از اکثر بافت ها را در خون حمل می کند. آمینواسیدهایی که در بافت کبد شکسته می شوند آمین خود را به شکل گلوتامات منتقل می کنند. از بافت عضلانی انتقال آمین به شکل اسید آمینه آلانین انجام می شود.
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Step 2 Carbamoyl phosphate condenses with the amino acid ornithine to produce the amino acid citrulline Occurs in the mitochondria Catalyzed by ornithine transcarbamoylase
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Step 3 Citrulline is transported to the cytoplasm
Condenses with aspartate to produce argininosuccinate Catalyzed by argininosuccinate synthase Requires energy released by ATP hydrolysis
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Step 4 Argininosuccinate cleaved to produce the amino acid arginine and fumarate of the citric acid cycle Reaction catalyzed by argininosuccinate lyase
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Step 5 Final reaction hydrolyzes arginine to generate urea – the reaction product that is excreted Reaction also regenerates ornithine, the original reactant in the cycle Reaction is catalyzed by arginase
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Urea Cycle Aspartate and carbamoyl phosphate each deliver an amino group to the cycle. Notice that the carbamoyl phosphate production and condensation occur in the mitochondrial matrix. 2
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بخشی از سیکل اوره در سیتوپلاسم وبخشی در میتوکندری است
1 L-Ornithine 2 carbamoyl phosphate 3 L-citrulline 4 argininosuccinate 5 fumarate 6 L-arginine 7 urea
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Regulation N-Acetyl glutamic acid
The synthesis of carbamoyl phosphate and the urea cycle are dependent on the presence of NAcGlu, which allosterically activates CPS1. Synthesis of NAcGlu by NAGS, is stimulated by both Arg, and Glu, both of which are elevated when free amino acids are elevated. So, Arg is not only a substrate for the urea cycle reactions but also serves as an activator for the urea cycle.
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Normal level of Blood Urea
BUN( Blood Urea Nitrogen): 7–21 mg/dL Urea [mg/dL]= BUN [mg/dL] * 2.14 Urea=
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Urea cycle disorders: در خون اوره کاهش یافته – آمونیاک (NH4+) افزایش
Anomalies of the urea cycle: N-Acetylglutamate synthase deficiency Carbamoyl phosphate synthetase deficiency Ornithine transcarbamoylase deficiency Hyperornithinemia, hyperammonemia, homocitrullinuria syndrome (HHH syndrome, ornithine translocase deficiency) Citrullinemia Argininosuccinic aciduria Argininemia این سایت را ببینید:
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افزایش اوره: Azotemia: elevated conc. of urea in blood
Very high plasma urea concentration accompanied by renal failure is called uremia, or the uremic syndrome Causes of urea plasma elevations are: Prerenal Renal and postrenal
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سرنوشت اسکلت کربنی:
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حدواسط های متابولیکی که از اسکلت کربنی اسیدهای آمینه ساخته می شوند:
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Fate of Carbon skeleton of amino acids: a keto acids
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تقسیم بندی سرنوشت اسکلت کربنی اسیدهای آمینه:
In humans, the glucogenic amino acids are: Amino acids that are both glucogenic and ketogenic: In humans, the Ketogenic amino acids are: Glycine Serine Valine Histidine Arginine Cysteine Proline Alanine Glutamate Glutamine Aspartate Asparagine Methionine Isoleucine Threonine Phenylalanine Tyrosine Tryptophan leucine Lysine
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تمرین: Write the equation for the transamination reaction between valine and pyruvate. Write the equation for the transamination reaction between phenylalanine and oxaloacetate. What products are formed in the oxidative deamination of glutamate? Determine if each amino acid is glucogenic, ketogenic, or both. phenylalanine leucine serine asparagine tyrosine valine
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