| Aspect | Functional-annotation fact | Evidence |
|---|---|---|
| Verified identity | **bgt** in **Enterobacteria phage T4** encodes **DNA beta-glucosyltransferase (BGT; EC 2.4.1.27)**, the enzyme responsible for the **beta** glucosylation branch of T4 DNA hydroxymethylcytosine modification. | (pqac-00000001, pqac-00000002) |
| Reaction | Transfers glucose from **UDP-glucose** to **5-hydroxymethylcytosine (5hmC/HMC)** in duplex T4 DNA, yielding **β-glucosyl-5-hydroxymethylcytosine** in DNA plus UDP. | (pqac-00000000, pqac-00000001) |
| Donor substrate | **UDP-glucose (uridine diphosphoglucose; host-supplied)**. | (pqac-00000001, pqac-00000002) |
| Acceptor substrate | **5hmC-containing duplex DNA**; acceptor binding is primarily associated with the **N-terminal domain** of BGT. | (pqac-00000000) |
| Product | **β-glucosylated 5hmC** residues in phage DNA; in T4 this contributes to the glucosylated-hmC genome state. | (pqac-00000000, pqac-00000002) |
| Catalytic mechanism | **Inverting glycosyltransferase** using a **direct in-line displacement** mechanism with oxocarbenium-ion-like transition-state character. | (pqac-00000000) |
| Catalytic residue | **Asp100** is identified as the **catalytic base**; the **D100A** mutant blocks normal catalytic behavior and was key to mechanistic assignment. | (pqac-00000000) |
| Structural fold / domains | BGT adopts the **GT-B fold** with **two domains** separated by a central cleft; donor nucleotide-sugar binds mainly the **C-terminal domain**, and a hinge around **residues 166-172** supports domain movement. | (pqac-00000000, pqac-00000001, pqac-00000007, pqac-00000008) |
| DNA-binding features | The enzyme surface includes a **positively charged concave region** consistent with binding DNA substrate. | (pqac-00000001) |
| Biological role in T4 | Performs **post-replicative glucosylation** of T4 hydroxymethylcytosine-containing DNA as part of the phage DNA protection system. | (pqac-00000001, pqac-00000002) |
| Anti-restriction role | Glucosylated hmC (**ghmC**) helps protect T4 DNA from many host nucleases/restriction systems; recent work shows ghmC can abolish or reduce several E. coli antiphage nuclease defenses. | (pqac-00000002, pqac-00000003) |
| Pathway context | Upstream, T4 first replaces cytosine with **5hmC** during DNA synthesis; BGT then modifies a subset of those residues after replication. | (pqac-00000002) |
| Modification fractions in T4 DNA | In wild-type T4 DNA, approximately **70%** of hmC residues are **α-glucosylated** and **~30%** are **β-glucosylated**. | (pqac-00000002) |
| Distinction from α-GT | **α-GT** acts immediately after replication but cannot modify neighboring hmC residues efficiently; **BGT** completes modification of sites left unmodified by α-GT. | (pqac-00000002) |
| Modern application: epigenetics workflows | T4 βGT is widely repurposed to **glucosylate/protect 5hmC** in enzymatic sequencing and hydroxymethylation-mapping workflows, enabling selective readout of cytosine modifications. | (pqac-00000004) |
| Modern application: cfDNA/5hmC detection | Reviews of 5hmC detection methods describe **T4-βGT-mediated glucosylation** as a core step for protecting or labeling 5hmC in cancer cfDNA and related assays. | (pqac-00000004) |


*Table: This table summarizes the core functional-annotation points for Enterobacteria phage T4 DNA beta-glucosyltransferase (bgt/P04547), including reaction chemistry, mechanism, structural features, biological role, and modern assay applications. It is useful as a compact evidence-backed reference for annotation and report writing.*