Enzymes that deaminate cytidine to uridine play an important role in a variety of pathways from bacteria to man. Ancestral members of this family were able to deaminate cytidine only in a mononucleotide or nucleoside context. Recently, a family of enzymes has been discovered with the ability to deaminate cytidines on RNA or DNA. The first member of this new family is APOBEC1, which deaminates apolipoprotein B messenger RNA to generate a premature stop codon. APOBEC1 has the conserved active site motif found in Escherichia coli cytidine deaminase. In addition, APOBEC1 has a unique motif containing 2 phenylalanine residues and an insert of 4 amino acid residues across the active site motif. This motif is present in APOBEC family members including activation-induced cytidine deaminase (AID), APOBEC2, and APOBEC3A through APOBEC3G. AID is essential for initiating class-switch recombination, somatic hypermutation, and gene conversion. The APOBEC3 family is unique to primates. APOBEC3G is able to protect cells from human immunodeficiency virus and other viral infections. This function is not unique to APOBEC3G; other APOBEC3 family members also have this ability. Overexpression of enzymes in this family can cause cancer, suggesting that the genes for the APOBEC family of proteins are proto-oncogenes. Recent advances in the understanding of the mechanism of action of this family are summarized in this review.

中文翻译：

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胞苷脱氨酶概述。

将胞苷脱氨为尿苷的酶在从细菌到人的多种途径中起重要作用。该家族的祖先成员只能在单核苷酸或核苷的情况下使胞苷脱氨基。最近，发现了具有使RNA或DNA上的胞苷脱氨基的能力的酶家族。这个新家族的第一个成员是APOBEC1，它可以将载脂蛋白B信使RNA脱氨基以生成过早的终止密码子。APOBEC1具有在大肠杆菌胞苷脱氨酶中发现的保守的活性位点基序。此外，APOBEC1具有一个独特的基序，其中包含2个苯丙氨酸残基，并且在整个活性位点基序上插入了4个氨基酸残基。该基序存在于APOBEC家族成员中，包括激活诱导的胞苷脱氨酶（AID），APOBEC2和APOBEC3A通过APOBEC3G。AID对于启动类开关重组，体细胞超突变和基因转化至关重要。APOBEC3家族是灵长类独有的。APOBEC3G能够保护细胞免受人类免疫缺陷病毒和其他病毒感染。该功能不是APOBEC3G独有的。其他APOBEC3系列成员也具有此功能。该家族中酶的过表达会导致癌症，这表明APOBEC家族蛋白的基因是原癌基因。在这篇综述中总结了对这个家族的作用机制的理解的最新进展。其他APOBEC3系列成员也具有此功能。该家族中酶的过表达会导致癌症，这表明APOBEC家族蛋白的基因是原癌基因。在这篇综述中总结了对这个家族的作用机制的理解的最新进展。其他APOBEC3系列成员也具有此功能。该家族中酶的过表达会导致癌症，这表明APOBEC家族蛋白的基因是原癌基因。在这篇综述中总结了对这个家族的作用机制的理解的最新进展。