金宝博正网> Nucleobase

核麻痹

Definition

名词
plural: nucleobases
biochemistry)基地nucleic acid那e.g.嘌呤pyrimidineS.

细节

概述

核酸是由核苷酸单体单元组成的生物聚合物。构成核酸的每个核苷酸由磷酸S.ugar(5碳),和核麻痹。核酸中的核苷酸链通过3',5'磷酸二酯键连接。这意味着用邻接核苷酸的3'-羟基酯化的5'-磷酸酯酯化。
核碱基是含氮化合物。他们也可以形成nucleoside当它们连接到五碳糖时核糖or脱氧。核苷是组分nucleotideS.。Nucleotide is the monomeric unit of nucleic acid, e.g.DNAandRNA。在两股核酸DNA,诊断eobases are paired. The two nucleobases that are complementary are connected by a hydrogen bond.

Classification

The nucleobases can be grouped into two major forms:嘌呤S.andpyrimidineS.。虽然嘌呤和嘧啶都是杂环芳族化合物,但它们可以基于化学结构彼此不同。嘌呤发生成两个碳环,而嘧啶作为一个碳环发生。嘌呤具有与咪唑环融合的嘧啶环。嘧啶只有嘧啶环。因此,嘌呤具有四个氮原子,而嘧啶具有两个。
Purines areadenineandguaninewhereas the nitrogenous bases of pyrimidines are胞嘧啶thymine那anduracil。These five nitrogenous bases are regarded asprimaryorcanonicalS.ince they are the fundamental units of the genetic code. The nitrogenous components are one of the major distinctions used to distinguish DNA from RNA molecules. In DNA, thymine complementary pairs with adenine whereas in RNA, uracil matches with adenine. The thymine differs from uracil in having a methyl group, which the uracil lacks.

Canonical nucleobases

The nucleobases adenine (A), cytosine (C), guanine (G), thymine (T), and uracil (U) are referred to asprimaryorcanonical。它们是遗传密码的基本核酶。DNA具体具有A,C,G和T,而RNA具有A,C,G和U.因此,区分DNA与RNA的方法之一是胸腺嘧啶的存在。DNA而不是Uracil,DNA含有腺嘌呤的胸腺嘧啶。与DNA和RNA的鸟嘌呤的核碱酶胞嘧啶对。将核碱基C-g的配对和A-T(或RNA中的A-U)称为基础补充
DNA为什么DNA具有胸腺嘧啶代替尿嘧啶的一个可能的解释与胞嘧啶转化为尿嘧啶自发的脱节。Cytosine can turn into uracil when it loses its amine group. This deamination of cytosine is a common occurrence. Nevertheless, the error is corrected through an inherent DNA repair systems. If not repaired though, it could lead to a点突变。如果在DNA中存在尿嘧啶,则修复系统可能无法将原始尿嘧啶与胞嘧啶转向尿嘧啶区分开,因此可能无法辨别尿嘧啶。胸腺嘧啶中甲基的存在(在尿嘧啶中不存在)有助于避免这种情况,从而保持遗传密码的完整性和稳定性。

非初级核碱基

The nucleic acids may contain other nucleobases. Examples of non-primary pyrimidine nucleobases are5.-methylcytosine(m5.C),5.那6-dihydrouracil那and5.-hydroxymethylcytosine。至于非初级嘌呤核酸酶,hypoxanthine黄嘌呤那and7.-Methylguanine是例子。

non-primary pyrimidines nucleoside 特征
5.-Methylcytosine 5.-Methylcytidine (m5.C) 修饰的胞嘧啶,即甲基化胞嘧啶
5,6-二氢水库 二氢库(D) A modified uracil

尿嘧啶分解代谢中的中间体
5-羟甲基胞嘧啶 来自胞嘧啶
non-primary purines nucleoside 特征
缺氧素 inosine(i) 修饰的腺嘌呤
Xanthine Xanthosine (X) 一个改进的鸟嘌呤
7.-Methylguanine 7.-Methylguanosine (m7.G) 一个改进的鸟嘌呤

m5.C是DNA中最常见的非原发性核酸酶,而ψ,d,i和m7.G发生在RNA(特别是TRNA)中。缺氧素可以从腺嘌呤的自发脱色形成。同样,黄嘌呤是一种嘌呤核酸酶,其通过脱氨基形成,但在这种情况下,鸟嘌呤。其他黄嘌呤来源是hypoxanthine(via the enzymatic activity of黄嘌呤氧气压酶) andXanthosine.(via嘌呤核苷磷酸化酶)。诱变诱变的存在可以促进缺氧酮和黄嘌呤的形成。特别是缺氧素可能出现错误的碱对,因为其与腺嘌呤的象征性(与胸腺天然对)。当发生这种情况时,DNA修复的方式之一是基础切除修复机制由酶发起N-methylpurine glycosylase

人工核酶

Certain nucleobases are artificially produced. Examples of nucleobase analogues areisoguanineand异孔苷。Isoguanine is an isomer of guanine that can be produced by oxidative damage to DNA. One of its applications is for use as a nucleobase inHachimoji核酸。异髓苷是胞嘧啶的异构体,其可以由胍和苹果酸合成。其中一个用途是用作核碱基Hachimoji RNA.

常见的生物反应

常见的生物反应

Ribonucleotides(即附着于核糖5-磷酸的核碱基)是核碱基的前体。嘌呤如腺嘌呤和鸟嘌呤衍生自核苷酸肌苷单磷酸盐(IMP)。反过来,否定是由a形成的核糖磷酸盐
生产嘧啶的生物合成途径之一是de novo synthesis pathway。在De Novo合成中,首先合成六个构件环并以尿苷一磷酸(UMP)的形成结束。六个主要步骤如下:1

  1. Carbamoyl phosphate synthesis
  2. Carbamoyl aspartate synthesis
  3. 环闭合,得到二氢酸盐
  4. Addition of ribose phosphate moiety
  5. Decarboxylation to yield UMP

Down in the biosynthetic pathway,uridine triphosphate(UTP),胞苷三磷酸(CTP), andthymidine triphosphate(TTP) are produced as catalyzed by certain enzymes.

常见的生物反应

嘧啶降解到CO中2那water, and urea. The metabolic fates of pyrimidines are as follows:

  • Cytosine » uracil » N-carbamoyl- β-alanine » β-alanine, CO2, and ammonia
  • Thymine » β-aminoisobutyrate » » Citric acid cycle

至于嘌呤鸟嘌呤和腺嘌呤,它们通常如下退化:

  • Guanine (viaguanase)»黄嘌呤(通过黄嘌呤oxidase) “ 尿酸
  • Adenosine »» inosine (via嘌呤核苷磷酸化酶)»缺氧(通过黄嘌呤oxidase)»黄嘌呤(通过黄嘌呤oxidase) “ 尿酸
  • Purines from catabolism may be salvaged and re-used as follows:

    • Adenine is salvaged by the enzyme腺嘌呤磷酰基转移酶(APRT)
    • 鸟嘌呤和缺氧是由酶挽救的hypoxanthine-guanine phosphoribosyltransferase(HGPRT)

    Biological importance

    The nucleobases are one of the fundamental components ofnucleic acidS,如DNA。核酸如DNAandRNAmolecules contain the genetic information that are important for all cellular functions and heredity.

    补充

    Etymology

    • 起源:Word(translation那“meaning”)

    Synonym(s)

  • nitrogenous base
  • nitrogen base
  • 进一步阅读

    也可以看看

    Mention(s)

  • 亚源化
  • Reference

    1. “Pyrimidine Synthesis”. (2017, May 3). Biochemistry Den. Retrieved from Biochemistry Den website:://www.biochemden.com/pyrimidine-synthesis/链接

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