Here you go. This is a code snippet to get the sys_id of the catalog item

var cat_id='';

if(email.body.item != undefined && email.body.item!='') {

  var item=email.body.item.trim();

var gr= new GlideRecord('sc_cat_item');

gr.get('name',item);

cat_id=gr.getValue('sys_id');

}