【正文】 nylalanine tyrosine Phenylalanine metabolism 2022/10/23 83 1. Catecholamine/melanin Tyr metabolism 2022/10/23 84 NH3+ | CH2 CH COO CH2 COO HO OH Homogentisate NH3+ | CH2 CH COO HO Tyr Phe Hydroxylase O || CH2 C COO HO Tyr aminotransferase 尿黑酸 對(duì)羥基丙酮酸 Tyr Catabolism 2022/10/23 85 CH2 COO HO OH Homogentisate OOC CH = CH C CH2 C CH2 COO || || O O cis OOC CH = CH C CH2 C CH2 COO || || O O trans H || OOC C = C COO + H3C C CH2 COO H O acetoacetate fumarate 尿黑酸 乙酰乙酸 延胡索酸 2022/10/23 86 ? Phenylketonuria (PKU) = lack of phenylalanine hydroxylase can’t hydroxylate phenylalanine to tyrosine Phenylalanine Hydroxylase amp。 PKU [Phe] = mM normally ? mM in PKU 1 in 20,000 homozygous 1 in 150 heterozygous IQ study: 53 ? 93 2022/10/23 87 ? People with phenylketonuria must avoid excess phenylalanine, but both tyrosine and phenylalanine are essential amino acids, so they shouldn’t exclude it pletely or brain disorders with result 2022/10/23 88 V. The Metabolism of Branched Chain Amino Acids ? Branchedchain amino acids (BCAAs): isoleucine, leucine and valine ? The catabolism of all three BCAAs initiates in muscle and yields NADH and FADH2 which can be utilized for ATP generation 2022/10/23 89 Isoleucine / Leucine / Valine ?keto acid ?ketoSCoA ?ketoglutarate glutamate transamination NAD+, CoASH NADH, CO2 ?keto acid dehydrogenase (if Leu or Lys, only this path can be used) ketogenesis ProprionylCoA SuccinylCoA gluconeogenesis A metabolic block here causes maple syrup urine disease 丙酰 CoA 2022/10/23 90 ? Most nitrogen metabolism pathways are very plex require many steps require input of ATP and NADPH are regulated by feedback inhibition mechanisms (allosteric) 2022/10/23 91 選擇題練習(xí) 氨基酸代謝 2022/10/23 92 1. 體內(nèi)氨基酸脫氨基的主要方式是 ( ) A 轉(zhuǎn)氨基 B 聯(lián)合脫氨基 C 氧化脫氨基 D 非氧化脫氨基 E 脫水脫氨基 2022/10/23 93 2. 體內(nèi)氨的主要代謝去路是 ( ) A 合成尿素 B 生成谷氨酰胺 C 合成非必需氨基酸 D 滲入腸道 E 腎泌氨排出 2022/10/23 94 3. 關(guān)于胃蛋白酶 ,不正確的是 ( ) A 以酶原的方式分泌 B 由胃粘膜主細(xì)胞產(chǎn)生 C 可由鹽酸激活 D 屬于外肽酶 E 具凝乳作用 2022/10/23 95 4. 關(guān)于一碳單位代謝描述錯(cuò)誤的是 ( ) A 一碳單位不能游離存在 B 四氫葉酸是一碳單位代謝輔酶 C N5CH3FH4是直接的甲基供體 D 組氨酸代謝可產(chǎn)生亞氨甲基 E 甘氨酸代謝克產(chǎn)生甲烯基 2022/10/23 96 5. 氨基酸脫羧的產(chǎn)物是 ( ) A 氨和二氧化碳 B 胺和二氧化碳 C ?酮酸和胺 D ?酮酸和 氨 E 草酰乙酸和 氨 2022/10/23 97 6. 哪種物質(zhì)缺乏會(huì)引起白化病 ? A 苯丙氨酸羥化酶 B 酪氨酸轉(zhuǎn)氨酶 C 酪氨酸酶 D 酪氨酸脫羧酶 E 酪氨酸羥化酶 2022/10/23 98 7. 血氨升高的主要原因是 ( ) A 體內(nèi)氨基酸分解增加 B 食物蛋白質(zhì)攝入過多 C 腸道氨吸收增加 D 肝功能障礙 E 腎功能障礙 2022/10/23 99 8. 氨基酸徹底分解的產(chǎn)物是 ( ) A 胺 ,二氧化碳 B 二氧化碳 ,水 ,尿素 C 尿酸 D 氨 ,二氧化碳 E 肌酸酐 ,肌酸 2022/10/23 100 9. 甲基的直接提供體是 ( ) A S腺苷甲硫氨酸 B 甲硫氨酸 C 同型半胱氨酸 D 膽堿 E N5CH3FH4 2022/10/23 101 10. 哪種酶先天缺乏可產(chǎn)生尿黑酸尿癥 ? A 酪氨酸酶 B 尿黑酸氧化酶 C 酪氨酸轉(zhuǎn)氨酶 D 酪氨酸羥化酶 E 苯丙氨酸羥化酶 2022/10/23 102 11. Which one is glucogenic and ketogenic amino acid? ( ) A Gly B Ser C Cys D Ile E Asp 2022/10/23 103 12. The ALT most active tissue is ( ) A blood serum B cardiac muscle C spleen D liver E lung 2022/10/23 104 12. The ALT most active tissue is ( ) A blood serum B cardiac muscle C spleen D liver E lung 2022/10/23 105 13. The average value of nitrogen content in proteins is ( ) A 10% B 15% C 16% D 18% E 24% 2022/10/23 106 14. The vitamine joining in methionine cycle is ( ) A B1 B PP C B12 D B6 E B2 2022/10/23 107 15. ?酮酸的代謝去路有 ( ) A 可轉(zhuǎn)變?yōu)樘? B 可轉(zhuǎn)變?yōu)橹? C 生成非必需氨基酸 D 氧化生成二氧化碳和水 E 生成必需氨基酸 2022/10/23 108 16. 蛋白質(zhì)消化酶中屬內(nèi)肽酶的有 ( ) A 胃蛋白酶 B 胰蛋白酶 C 氨基肽酶 D 羧基肽酶 E 彈性蛋白酶 2022/10/23 109 17. 可生成或提供一碳單位的氨基酸有 ( ) A 絲氨酸 B 組氨酸 C 甘氨酸 D 色氨酸 E 甲硫氨酸 2022/10/23 110 18. 嘌呤核苷酸循環(huán)中參與的物質(zhì)有 ( ) A 草酰乙酸 B ?酮戊二酸 C 腺嘌呤核苷酸 D 次黃嘌呤核苷酸 E 蘋果酸 2022/10/23 111 19. The amino acids which join in ornithine cycle are ( ) A aspartic acid B citrulline C Nacetylglutamic acid D arginine E ornithine 2022/10/23 112 20. The main transporting forms of ammonia between tissues are ( ) A urea B ammonium ion C ammonia D alanine E glutamine 2022/10/23 113 The end